Originally Posted by LATECH
Dont spend money on roller rockers. They wont do anything for performance on a street build.
The 78 block is most likely the 557 block. It will be an OK block, but if your building in excess of 400 horses the older block would be better.
If it were mine, I would sell the 557 as a buildable core, and use the money to get what is needed to put the other one in the car.
LATECH is correct, the 1971 block is a stronger offering from GM, even if you don't plan on building 400 HP or more it never hurts to have a stronger building block to start from.
Roller rockers, again correct, as I mentioned earlier no noticeable power gains on "semi mild" street engines, if you venture to go to a roller cam, then a roller rocker would be something to look into.
You are fortunate that you do have a 1978 block and again LATECH is correct, get some cash from the sale and make your 71 sing.