Are you talking MC(moved centerine of the valves)thats only B1 stuff and the MC head.If oyu are talking spread bore then Indy make a 4.84 BS block that uses a 600-13 head. You can also get spread bore stuff in the form of B1 TS on a Donovan or KB block. they come in 4.8, 4.84and 4.9bore space varieties. Then as mentioned there is the pro stock stuff with is 4.9, and 5" stuff