New guy with a new project

You'll need to cut down the driveshaft length, the 727 is longer than the 904.

Swap mounts by Trans Dapt can be used cheaply instead of the Shumaucher (Engineswaps.com) mounts. You'll just need the proper motor mounts. At this point, I'd go back to engineswaps.com and get there interlocking motor mounts.

IMO a 8-1/4 size rear will hold up to a very decently powered engine without the expense of a 8-3/4. If not so allready equiped. The backing plates and etc... hardwear will swap over from most any car. Just order theparts from what you swapped it from since drum depth can change sometimes. Not all 8-1/4's have 2 -1/2 deep drums.
I swap on 11 inch drums from a Cordoba onto my '74 Duster 8-1/4 rear. It's a bolt on, but you need the backing plate to start with. Donor car time.

Front disks can be had from other A body cars or you can use late B body spidles and upper A arms. (AKA example would be a 79 Cordoba)

Theres also a few places around in the mag's like SSBC that have full kits for the street, Wilwood for race kits.