The 4.3 and 5.7 use the same flywheel and bellhousing bolt pattern and the '89 V-6 and V-8 C1500's both use the Getrag. The Getrag in my 4.3 '89 C1500 is the same as the 5 speed in a '96 4.3 S-10 although they changed the designation slightly and call it something else, IIRC it is now referred to as a New Process but it's still the Getrag. My friend owns a transmission shop and verified it for me becuse I was looking at a wrecked '96 S-10 for parts for the 4.3 and 5 speed for my '89 but the '96 is a "true" Vortec and my TBI wouldn't work on it without way more work than the truck is worth. I should have bought it just for the trans but didn't.............. oh well. Now a 3/4 ton fullsize may be a different story. I didn't check that.