I put my old M & A heads onto a 109 block this past winter. The heads came off my stage block.
I was able to reuse some of the studs but to find the length of the few I still needed I put a little 90 degree bend onto the end of a wire and stuck it down through the head and deck until it hooked under the threads in the block. Then I measured the wire and added the thickness of a washer and nut and ordered that length directly from ARP.
Dunno if this is the proper way of doing it but it seemed to work.
Chris