The blocks are interchangeable if they both are 6 bolt bellhousings.
I would build a 302 cube, never a 289. There is 16 hp and 16 lb ft torque difference..... apples to apples....
the heavier crankshaft is basicly irrelavent.
I prefer the 5.0 pistons in a 302. The narrower rings make more power. CompCams XE 268 H cam. Performer RPM intake, Edelbrock 600 carb.
If you have offset piston pins, Joe Sherman insists that on a 302 it is worth another 20/20 or more to install the pistons with the pin offset backwards.
The 289 closed chamber heads properly done with big valves are worth another 30 hp.
Joe Sherman is the guy who gets 400+ hp out of factory iron headed 302s with pretty mild camshafts...