I have a saginaw 3 speed on the tree and was thinking about putting a 4 speed in it and keeping it on the tree. My plan was to just swap out the trannys (since I've heard they're interchangeable) and hook it back up normally and just make a separate lever through the floor for reverse. I've been looking between saginaws and muncies and I know muncies are lighter and pre-71s are interchangeable with saginaws but I've heard good and bad about both like how people have torn on saginaws and never broke em and how they've broken teeth in muncies. Besides saving 30lbs, is there any advantage to spending the extra $400 on a muncie?
The Saginaw was GM's light duty transmission and was usually installed in cars with under 300hp, although I have a friend who had a Saginaw in a `69 big block Nova and he abused that car like no other and he never broke that transmission. If you're on a budget and you're not building a race car then I see no reason not to use the Saginaw for your first project and put the extra money somewhere else in the car. One thing to be aware of is the Saginaw transmissions have a wider variety of gear ratios, some of them up over 3.00 for 1st. Most of these came in cars like the Vega, etc., and will be the weakest of them all. Try to find one with a 2.54 1st gear and you'll be fine.
I've got a rebuilt BW Super T-10 out of a '78 Z28 (3-grooves input shaft spline) I'll sell you for $600.
