what spark plugs to use

IMHO best series of plugs for lower compression LA
you can find in NGK if you really want to
RC12LYC Autolite 3895 985
RCN12LYC #412 5/8 hex
4412 Truck plug 5/8 hex
3034 Platinum
RN13LYC/RN13LYC5 #101/817 13/16 hex Autolight 3885
RFN14LYC hotter #82 5/8
If higher compression or High compression 340 read the plugs and check for interference with piston