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.