Not interchangeable, the old ford and Merc. o.d. trans are Borg Warner. They are the precursor to the T-10
I'm running a '39 style trans behind the Cadillac in my 40; no burn-outs and no speed shifts but 2nd gear is real fun on the on-ramp.
Thanks....hopefully went I get there - I have acquired a lot of the small back end gears in my trading around.
I have run both behind my FH. I prefer the T5. Just being able to shift into first while still rolling makes the T5 a better choice for me. That benefit is seldom mentioned in these conversations.