No one builds big blocks any more for factory cars. Technology lets small blocks make more power more efficiently. The only real reason for a big block these days is either nostalgia like was mentioned, or you just need a huge motor for a boat/drag car.

If you have access to one, you can make easy power with them. But the next guy with a similarly built small block will beat your ***. We live in an era where production small blocks are producing over 1,000hp in some cases, and these days over 400 is common from factory engines.

 

The saying used to be, 'the cure for a small block is a big block', which is still true for a few applications.
Now the it would be something like, 'the cure for a small block is a big inch small block'.

 

Or a turbo. Or nitrous. Or a higher rpm small block.

If you have a big block laying around, most of them make decent power with little effort not because of their size, but BB head designs were WAY better until the head market for small blocks took off.

Not surprisingly, some of the newer small block heads carry over features from big block designs of yesteryear.

 

How accessible are 351 rollers? Also if you are doing 65/66 302 better fit.

 

Later 351 truck engines were roller blocks.

 

Roller blocks are not required for a roller cam install. Just get the right cam and link bar lifters.