Drivetrain Questions and Suggestions

So I have a 73 Scamp, and now that my tax return came in, I have some extra money to help move my project along. Currently The car has the original 904 that is mated to the factory 318 with the factory 8.25 rearend. The transmission shifts fine and has started to leak from the front seal or whatever it is called.

So I am going to build a 360 for this car (another thread to come) and not sure which route to take. The 360 I bought came with a 727 from a van, so should I build the 727 or the 904? what is need for the 904 to work with 360 (externally balanced or something right?), and to run the 727 what else do I need besides to shorten the driveshaft.

As for the rearend should i build the 8.25 or a 8.75. my 8.25 currently works and is in the car, but is a non suregrip. I have 8.75 A body housing but no guts. Which one would be better/cheaper to build? What kind of case should I look for for 8.75? This is all new to me. Keep in mind I only have about 1800 to spend on drive train,but plan on doing as much work as I can to keep price down.

Thanks for any input