well, there's your problem-- you have a BFH in your engine!
all kidding aside, RRR is on the money. i'd sit down and run the numbers to see how much dosh it would be to make those heads work for what you want/need vs what a new aluminum set would run ya.
Yeah and don't forget to add in the extra cost to get the new aluminum heads checked out. There's no way in heck I'd bolt any of them on out of the box. As @318willrun about that.