The firing pin is specially made for the 7.62X39 and is slightly longer than the AR-15 firing pin. Here's one from PSA #505873. Use a standard spring set for the trigger group.

7.62X39 (extended) firing pin, Carbine Buffer Spring, higher power hammer springs

Buffer spring is entirely dependent on buffer tube. Normal firing pin should be fine, but what may be an issue is the hammer spring. I would start with a milspec trigger group and look to change things if you are having problems with light primer strikes.