[Too Many Projects]

Originally Posted by Bill Pritchard

3.31 rear axle ratio was standard with the 3 speed manual, whereas 4 speed equipped cars got a 3.55, so there's a good chance this was an original 3 speed car. I too will be following along as you progress!

Would that have held for 1970 also ? I've had 4 '70 SS 4 speed cars and 3 of them had 3.31 ratio. The 4th was a 3.73. Of all the 12 bolts I've had over the years, I've never had a Chev 12 bolt with 3.55 gears, but all the 3.31's were M20's also. Maybe the M21 came with 3.55 ?