All of the advice above is great advice. What you need to understand is the reason for the differences. The H-M transmission is much larger so it was designed so that it could be removed from under the truck for service. Therefore the larger crossmembers that unbolt to clear the transmission to drop it out. The brake line routing is different for that reason. It goes behind the end of the transmission so that it is not in the way when the transmission is dropped out below, The trans cover Jorb mentioned gives access to the bellhousing bolts. All for a reason and that reason is serviceability. The H-M has a solenoid starter instead of the stomp starter. It has an automatic choke carb instead of the manual choke for a manual trans. There is a neutral start switch that mounts to the steering column. Chevy and GMC use different linkage and neutral start switch setups and are not interchangeable. Tim mentioned the driveshaft length difference. The engines and transmissions were matched at the factory in that they were align bored together. The transmission can be used on a different engine as long as run-out checks are made and corrections made with offset dowel pins to keep the transmission from shaking itself apart. I am going to send you some contact info in a private message of someone that helped me a lot in shipping a transmission and parts around the country.