The heads should fit along with the exhaust manifolds. A 302 with the 351 cam and 4 barrel is good for at least 200 hp. If the 302 block is a roller cam engine then you should get an after market cam. Some brackets from the 351 may not fit the 302 because of the deck height. You will need the 302 flywheel and harmonic balancer along with the 302 distributor.
I would rather rebuild the 351.