Are the long head bolts for the later model engines the correct length? If so you only need to buy 4 bolts to complete the set. Dorman head bolts used to be available for individual purchase. If you can't find them that way, one option would be to purchase a second set of head bolts and use enough of the ones that are the correct length to complete the job. Head bolts don't know, or care what size engine they're in, as long as the length, thread engagement, and torque is correct.
Using studs the right length with nuts and hardened steel flat washers from ARP would be another, but much more expensive option.
Jerry
