If I were to do this, here is what I would do. Mock up the block and heads with head gaskets. Install timing cover and then see if the Mag acc bracket will fit. Does it hit the heads? Is there a gap? Get an indexing punch through the bracket holes and mark the heads. You'll need to have some solid stand offs made that will get welded to head (this is what KRC did with the Brodix heads and it's probably the best idea) and also spot face the back of the acc bracket the required amount. Basically drill a small 1/4" hole in the head about 1/8" deep at each mark. Make the standoffs 1/2" long with a register to fit in that hole. Have them welded to heads, then drill and tap the stand offs for whatever size bolt you wanna use to mount bracket. I suppose you could tap them before welding, but I'd leave a bolt in them to keep them from ovaling when welding.