I believe there are three teams using them. From what I saw at RWR those teams have multiple engines and parts. I recall pallets of heads and blocks at one point on the floor at RWR for one team.

Slawko's heads seem to be the best version going right now. Just not enough parts out there for many to persue this combo. There are a couple of comp teams but they either bought old Pro Stock truck operations or ran PST back in the day. The Mettler Brothers in Cali are one of those teams. From what Ive seen block prep pretty much what has already been said.