[blykins]

Yes, you would need difference pistons because of the Cleveland's canted valve arrangement.

The 4V heads will make some big horsepower....but they are way too large for a 289-302 street engine. Boss 302's (302W block and 4V Cleveland heads) made decent power back in the day, but it took some revs and a nice rearend gear to take advantage of it.

The 4V heads work really well on 351+ cubes. Also, the aftermarket is full of 4V replacement heads, with CHI and AFD being some of the heavy hitters.

CHI makes a "3V" head, which has the port velocity of a smaller port, but the flow of a larger port. They are available in 208cc, 225cc, and larger layouts, and they work perfect right out of the box. I just built and dyno'd a 408C with the 208cc 3V heads, 10.3:1, and a little solid roller cam and made 574hp.