I can only think of three reasons to consider using OE iron heads for a build like this.....

A- you already own a nice set of them, that have already been machined/ported/assembled with the components you require to reach your goals.

B- you are going to compete in a class where running OE iron heads is one of the requirements.

C- you have all the skills needed and equipment required to do the job yourself, and like doing that kind of work........ As well as a few sets of usable cores on hand.

Okay........ Maybe one more....

D- you have a car with some racing history and want to keep it as period correct as possible...... And accept that if none of A, B, or C from above apply, you're likely going to spend more money on the OE iron heads than you would if you bought certain aftermarket heads.