You do whatever makes money. I would move onto something like that too if I was him. The Ford head market has become too competitive. I think the crux of my argument is that anything you do a GT40P head you can do to an E7 and they flow about the same. I'm sure I could get my engine builder to machine up some nice 12 second E7 heads for under $400 with new valve guides and a fresh valve job. My old engine builder used to do a nice set of 12 second E7 heads for $300, but that was 90s prices.
Kurt
Kurt