71 'Stang/ new 351W/ orig. C4 compatability
 

My 71 Mustang was originally a 302. I've got a 351W to put in. Can I just bolt up my original C4? I've fitted it all together on the garage floor but I'm wondering if the flexplate counterweight unbalance factor is right. Murray

Should bolt up to 351W without a hitch. They should also be 28 oz imbalance too.

Just to follow-up. The 157 tooth flexplate has the same imbalance and will work with the 351W as long as the converter, bellhousing and engine plate match up. I had trouble with the engine plate. It was hard to find one I think because they haven't used the 157 tooth set up since ?73. The plate for the larger flexplate is almost the same except the starter hole is about 1/2" different. Murray