just remember....once the block is bored to its limits , bye bye block... If it already has never been done , like 6t5 gto said , let a good builder make that call after they look at the block.... good luck Daveby Dave Williams - Pontiac GTO Forum
fan is a standard 18 inch seven blade. part # 9777014 . Daveby Dave Williams - Pontiac GTO Forum
sorry marlan , I failed to remember the message, power steering pully is 9786900 ,by Dave Williams - Pontiac GTO Forum
you did not indicate if power steering was needed, top pully is 8 inch and part # is9790946 , bottom is 7 and 1/4 inch #9790947 , and the alt. pully is 2 and 3/4 inch #1949357 , but that should already be on the alt. Daveby Dave Williams - Pontiac GTO Forum
the 421 was made from 1961 thru 1966, also called a 421 sd, short for super duty , the 389 was made from1959 thru 1966 , 389 high performance motors made from 1964 thru 1966 , the 421 was only .030 bored over from the 389 , and has 4 bolt main caps , so in short , it is some what of a collecters item and hard to find , but a very good motor , I wish I had one.by Dave Williams - Pontiac GTO Forum