The transmission that I now have which will replace my saginaw, is a first generation st-10 with a 2.43 low gear ratio. I believe it to be a close ratio unit. Will this be compatable with my 3.55 rear end ratio, or, should I try to locate a wide ratio transmission? Thanks in advance.

Believe it or not, the Muncie wide box only had a 2.52:1 first gear. The close ratio Muncies had 2.2:1 first gears. If you're only running it on the street the Super T-10 should work fine. Just don't expect the 307 to knock you into the back seat from a dead stop.

The 2.43 ST 10 has a much better ratio spread than a M-21 M-22. I have had the same trans as yours in my 66 vette with assorted 468s for 25 years and had to do nothing to it.

Thanks for the information-it was quite helpful.
The 307 currently in the car will be replaced with a 1969 vintage 350, hence the need for the st-10!
Rhanks again!