small block to big block
Spend some time in the tech pages at Big Block Dart, especially:
http://www.bigblockdart.com/techpages/dck.shtml
In my opinion, every suspension/brake mod the car might need, it needs it for any performance build (being a 73 V8 car it should already have discs and possibly a sway bar). So, in the end the biggest expense will be in new exhaust if you go BB.