T-50 is the old borg warner chevy Monza tranny from the 70's.
So far I've come up with M-50 2 wheel drive 5 speed 1998 to 2005.
M-50 is a NV3500 ,1rst gear ratio=3.490 2nd=2.160,3rd=1.400,4th=1.000,5th=0.780.
Its a medium duty trans. used in every 4.3 litre vortec S-10/blazer from 1998 untill 2003.
If you want to read up on it search WILKEPEDIA for NEW VENTURE 3500.