Tom idk if this is of any help but my KB block was shipped with the studs and the engagement in the block was definitely deeper than common, not that it would be the same for both blocks. they're packed away at the moment if needs be i could dig them out and get measurements.

"normally" most studs aren't necessarily anything special they're just packaged as kits, i have on a number of occasions ordered loose studs from ARP. there is a normal ratio of thread length vs fastener diameter but i don't recall it at this time. the reason i mention this is that it seems to me the threads on the coarse portion that threads into the block was longer than normal so in this case they might be a special stud