Studs to bolt stock exhaust to aluminum heads

Can anybody tell me if I can get studs which are 5/16 coarse to go into my edelbrock aluminum heads and have the 3/8 fine thread to fill the holes in a stock 1970 340 manifolds for the nuts to go on. I have the two long tube nuts and they are 3/8" I don't see any in the ARP catalog unless I am overlooking them?