Obviously, your project = your choices.
However: have you a clear vision of the goal? Is the final power output, doing what you describe here, going to be sufficient? Is an L6 the only choice?
A 292 can produce a lot of power, but not a lot of power + better mileage. After perhaps 200 hp the street manners begin to go downhill along with the mileage. A 300 hp L6 is a very different car to drive than a 300 hp big block.
