I just put the T-5 behind my 261, 46 Chevy pickup and it's great. The T-5 is an aluminum case so much lighter weight that the cast iron Saginaw, would be just the ticket in your light roadster.
The T-5 can fit just about any Chevy bell housing, just takes some minor mods to the input shaft and front bearing retainer. You need to check out all the tech tips on this site.

Jim, I.I. #173
(It's easier to get forgiveness than permission!)