To be clear, I'm calling the part that bolts to the engine the mount, the part that bolts to the frame, I call the bracket.
With GM left side is usually an odd number, right side is even numbered. Of course if a part is reissued later it may have a much later number.
I have frame brackets for a 69 302, RH 3945508 is 1 7/16", LH 3945507 is 1 1/2" from frame to hole.
My 67 327/275 frame brackets are RH -3980938 is 2 1/4", LH -3955183 is 2".
69 high perf frame brackets were lowered to compensate for thicker motor mounts that are interlocking to prevent separation.
Low perf engines in 69 used the older non-interlocking mounts. I suspect the thick mounts were not available in large enough quantity for every engine, or they had a lot of the thin mounts in stock to use up.
I think later on, thin interlocking replacement mounts became available for the low perf and older applications. Energy Suspension makes thin and thick interlocking polly mounts.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer
[This message has been edited by davidpozzi (edited 10-30-2002).]