Should you part the 78, things you may want to upgrade earlier bikes.
Front end minus the trees, chrome all the way up, longer legs, can use fork brace.
Swingarm, if you dont mind 1 1/4 longer, and its a touch wider.
Rear wheel..17 inch.. Widest rear rim on the 750, still resembles front rim, its wider in the carrier.. But you can go back to the original width if you like.
Head.. Possibly better.. The studs are handy.
The carbs, if you want low price squirters, these fit the bill.
Probably a few more bits.