Building a new 505 With Callies / Mopar Performance Block

Correct, you'll most likely need to find Torx drive bolts that have a round head. Same kind of bolts that Jesel uses in some of their kits. Sometimes you can find an ARP bolt that will fit but usually the flange is too big. If you have a lathe you can turn down the ARP bolts to fit. We typically use a Torx head.
That's what I have done...chuck it in a lathe and cut the flange down!