[Jack21]

In days of old, when knights were bold.... '70's, early "Smog" motors' Ford guys would swap their 289 and 302 heads for 351W for bigger valves and better flow. That was then. (30 years ago)

Today, there are better ways of doing this. With a '91 roller block, you can get a decent set of late heads and build a nice carbureted or EFI motor.

Keep it simple for your first engine. There are enough ways of making mistakes with the simple stuff before you start playing mix & match.