Rear end selection help and opinions

Ok, so I'm wanting to finally get rid of my 2.76, 7 1/4" rear in my '71 Dart. It currently has a 300 hp(ish) 318, 904 transmission, 3000 stall, and small bolt pattern 9 inch brakes all around. What I would like to do is upgrade my rear with 3.54 gears and keep my sbp. That limits my choices greatly but there's still 8 3/4" and after market Dana 60s to choose from. I'd also like to have a direct bolt on rear since I am no fabricator and my choices locally are limited. At some point the 318 is going to come out and and possibly stroked or upped in compression and hopefully be in the 400 hp neighborhood.

With all that being said would ya'll just go with a Dr. Diff Dana 60 setup or piece by piece put together an 8 3/4"? Also, what would be your thoughts on brakes? I'd like to stick with drums in the rear and eventually I'll upgrade the 9" drums in front to discs but it stops decent now and I don't want to buy new wheels and tires.

The car is mainly just for fun and occasionally makes trips down the drag strip but that's about an hour away so highway driving happens and that's why the 3.54 gears. Thanks in advance!