Hello,

I have a pair of frame mounts that are suppose to be for a big block they came out of a 1969 Nova, but am not sure how to tell, but the number on the driver's side is 3945507, and the passenger is 3945508. Can anyone tell me if these are for a big block or not?

Thanks in advance.

Those are 1969 302-350. BBs are 3980941 & 3980942. LH BB frame mount is always taller than the RH; 67-68 BB frame mounts use the early style motor mount and are slightly wider than 69. Remember you will also need a BB crossmember (amnual/auto different) and clutch cross-shaft. For a 4-speed you could re-drill the monuting holes; the factory piece was different.

Thanks,

As long as I plan on running a turbo 350 transmission, then the stock crossmember will work? Is there any way to tell a big block crossmember, I have several and the cutout hole on the bottom of the crossmember(where the bolts go through to the trans. mount) are different, or is this just due to different years?

Thanks in advance

You may want to re-think the plan to run a TH350 behind a rat motor; unless it is race-prepped it won't last very long. Even automatic 1970 Z28s got T400s. The 350 uses the standard crossmember so it could be re-drilled; BB mounts offset the motor about 1" to the RH for clearance. The BB/manual piece looks just like the standard except the opening for bolt access has one angled corner; the standard opening is uniformly radiused. The bb/auto crossmember is formed from tubing and has a welded tab for the trans mount; probably only fits the T400.