I would like to know

Your welcome. And yea, it is a good honest question.
Like I said above, I’m not going to say “Yea, go run a cracked head.” Though mine don’t have an issue despite the cracks. There small, in between the seats, the valves seal, it’s in an area where there is no coolant. They still work. I’m sure my other 5.9 has cracks. I’ll be running it until further notice with no plans on doing anything about it.

Replacement heads are the iron “Replacement Head” or the two aluminum choice from Trick Flow or Edelbrock. There a crap load more expensive than the iron replacements which really aren’t any better performance wise over the OEM head. I guess you could split hairs there and make some points. I’m not talking about porting ether. Once you start porting the iron replacements, you might as well look into the aluminum heads for a cost vs performance bang for the buck.

I wouldn’t port the OEM heads unless the race rules said you must have an iron head. The aluminum choices are a Edelbrock home run or a Trick Flow grand slam. The only Magnum iron heads worth porting were (key word meaning past tense since there not made anymore) would be the Aussie’s EQ or MoPars R/T head.

Also, a 1.7 aftermarket rocker is available for the Magnum head.
Pop a 1.7 rocker on your LA camshafts watch that lift skyrocket. Do the math! Then use coat on your piston to check! LMAO!