Went fishing, snagged a Barracuda

From personal experience in getting my 67 Dart up and going, I would go ahead and just replace and keep the drum brakes for now. Unless you plan on going 4 wheel disc, the back wheels will already be done when you get the big fast engine lined up. However you are probably going from the 4 inch to 4.5 inch bolt pattern once you go with disc brakes.
The drum brake parts were actually very reasonable, I just paid $37 for a brand new Mastercylinder from Napa, now every single last brake part on the car has been replaced!

Nice find, good luck with the project.
BTW: I thought Lafayette, CO seemed familiar. My brother used to live in Longmont, absolutely love that area/region, want to go back on vacation some day.