Heads used on 327/350/383/400 SBC engines without steam holes is Felpro #1003. All Speedmaster 23deg. SBC heads use standard 14mm. x 750" reach, 5/8 hex, gasket seat sparkplugs like NGK R5671A-7, Autolite 3924, Champion RC12YC, etc.
Chevy SBC 350 205cc 64cc Straight Plug Bare Aluminum Cylinder Head
Chevy SBC 350 205cc 64cc Straight Aluminum Bare Cylinder Head
Chevy SBC 350 205cc 64cc Angle Aluminum Bare Cylinder Head