In order to understand what conversion mount you need for your project, you need to have a better understanding of Chevrolet V8 motor mounts for your vehicle. 

1973 was the first year for A-Bodies to transition from the Early Style SBC motor mounts to go to the Clamshell Style SBC motor mounts. 1974-77 all used the Clamshell Style.

Every SBC/BBC GEN 1 has the same exact bolt pattern on the block for motor mounts. They never changed the engine side. The following photo's through-bolt hole with the dotted line is the easiest measurement to use to compare with your existing setup. Measure the width of your Frame Perch and then match it with one of the following SBC Early Style motor mounts. 

Early Style SBC/BBC Gen 1 engine mounts available today are classified as Short and Wide or Tall and Narrow. They are typically mounted directly to a Frame Perch. 

1964-72 Chevelle with Energy Suspension Poly Short and Wides with our aluminum LS Double-D conversion mounts

A- Frame Perch, B- SBC Early Style Motor Mount, C- LS Conversion Mount

Generally the 1973 GM A-Bodies with a 5.0 307ci V8 used the 2142's and then the 6.6 400ci used the 2283's. You can use the dimensions and part numbers in the following photo to find out exactly what you are dealing with on your project.

Short And Wide

OEM Part Numbers(Rubber):   3990914,   3960768,   6258154

Aftermarket Part Numbers(Rubber):   2142,   2285,   2267

Energy Suspension (Poly): 3.1114 Zinc, 3.1115 Chrome (G-Black, R-Red) 

Tall And Narrow

OEM Part Numbers(Rubber):   3962740,   3990918,   3962748

Aftermarket Part Number(Rubber): 2283

Energy Suspension (Poly): 3.1117 Zinc, 3.1118 Chrome (G-Black, R-Red) 

Early Style SBC motor mounts on their matched Frame Perch. Notice how they are about identical in height in the end. 

The motor mount and motor mount bracket in the following photo goes by a lot of names. A and B make up the Clamshell Style engine mount. GM refers to A as engine mount and B as a bracket. Nowadays, A is most commonly referred to as engine mount while B is most commonly reffered to as the Clam Shell. Engine mount is a loose term however and in order to not confuse the style of motor mount you have with the Early Style, you can refer to them as the Clamshell Mount. A can also be referred to as: rubber isolator, rubber mount, SBC/V8 engine/motor mount, "mounting, engine". B can also be referred to as: buckets, elephant ears, cups, motor/engine mount bracket, "bracket, engine mount", "bracket, engine mt". The Clam Shell Style started to phase out the Early Style Short and Wide/Tall and Narrow's in 1972.

OER makes reproduction Clam Shells but you have to understand that they are not a one size fits all. 2WD and 4WD 1973-1987 C10 will not interchange for instance. If you are removing the Clam Shells for any reason, such as replacing the Clam Shell Mount, don't forget to label them as passenger and driver side so the install is much easier. 

The Clam Shell Mounts and the Clam Shells themselves will vary depending on application. SBC's typically used a 4-bolt Clam Shell Mount while the BBC's and Diesels used a 3-bolt Clam Shell Mount. If you have the Clam Shell Mount and the Clam Shell, you can use the conversion mounts already listed above. Some Clam Shells need to be sanded down to a flat surface before bolting them to the conversion mount unless using the DD-Sliders/DD-LT-Gliders.

4-bolt Style Clam Shell Mounts have mounting holes for bolts on all four corners. Often only three holes are used.

Not to be confused with the the 3 bolt style Clam Shell Mounts where they only have 3 mounting bolt holes. 

          A- Mounting bolt holes that are flush to the engine crossmember/V8 frame perch

          B- Rivets/welds holding the clamshell together. 

Generally the 3 bolt clamshell part number 2395 was only used on factory BBC 454 applications. All others used the 4 bolt clamshell part number 2292.

4 Bolt Style 

OEM GM Rubber- 14039437, 9762326, 467422, 1001132, 10001133, 9764714, 459021

Aftermarket Rubber- 2292

Poly Insert  3.1116 (G-Black, R-Red)

3 Bolt Style

OEM GM Rubber-  14071939, 22145334, 22188393, 334941, 357717, 3993721

Aftermarket Rubber- 2395

Poly Insert 3.1121 (G-Black, R-Red) 

*We only carry the black (G) versions as they are self-lubricating. If you want red inserts, replace the G with an R and you will be able to find them. 

If you can't find a complete frame side and engine side V8 Chevy motor mounts for your application, then check out this Clam Shell Mount Method.

LS GEN III/IV Conversion Mount Options:

*Designed for 1973+ Clam Shell Style

*Does NOT require Clam Shell

*Will NOT work with Early Style SBC frame perches

DD-6500C

*Designed for 1973+ Clam Shell Style

*Does NOT require Clam Shell

*Will NOT work with Early Style SBC frame perches

LS Oil Pan Options:

F body pans with a modfication to the front of the sump will fit. These Holley pans are basically modified F body pans.

Holley 302-2

Holley 302-3

LT Oil pan Options:

Holley 302-20

Power Steering

 

All the way up to 1979, the factory gearbox takes an inverted flare fitting. It is quite common to find a newer gearbox isntalled with a metric o-ring fitting instead. Use the following information to figure out what fittings you need for your power steering lines. 

 

	Pressure	Return
LS Power Steering Pump	M16x1.5 O-Ring	Hose Clamp
Before 1980 Gearbox (SAE)	5/8"-18	11/16"-18
After 1980 Gearbox (Metric O-Ring)	M16x1.5 O-Ring	M18x1.5 O-Ring

 

 

*Photo's of gearbox's from Lee Power Steering

 

If your O-ring is old and hard, use the following part number for replacements: GM 26001594 

DO NOT use any O-ring you find at the parts store. The Metric O-Ring fitting requires an O-Ring made of Viton so the power steering fluid doesn't destroy them. 
O-Ring Technical Info: 903 (7.65mm ID x 1.63mm C/S or .301 ID x .064 C/S) Viton

 

If your vehicle has the Metric O-Ring fittings, then your power steering lines will bolt straight up to any power steering pump offered in an LS application. Make sure there isn't an O-ring already in the power steering pump from the old line!

 

If your vehicle has the SAE fittings AND the 3/8" lines line up to the back of your LS power steering pump, all you need is THIS ADAPTER to be threaded into the high pressure port on the pump. The power steering pump side is M16x1.5 with a Viton O-Ring while the power steering line will fit a 5/8"-18 Inverted Flare. 

 

3/8" Line threaded into the adapter fitting on the back of an LS truck power steering P pump with THIS ADAPTER

 

 

 

 Check out Lee Power Steering for all your GM gearbox needs. They can rebuild and do precise valve tuning to give you that exact steering you are looking for! 

 

How to Identify Your GM Gearbox

 

 

Power Steering Ratio Feel Explained