If I remember right they are 1/4-20 right?? if they are some off of a 454 91'-5' truck would probably work. it has aluminum valve covers and the bolts have the little "bats" and 3/8"heads. I have also used allen head cap screws before on my M/Ts and they looked nice.
besides they stayed pu and didnt turn like the stems and wingnuts did
its looking pretty good