I have an early 70's Detroit 453N engine with a bad head. I have a good head on an identical engine but it has N45 fuel injectors where as the old original head has N50 fuel injectors. Can I just use the new head with the N45's or should I put the N50's from the old head in the replacement head? And if I should want to put the N45's in can I still use the old injector tubes? Thanks for any help.