For clarity:
Are these used factory production Magnum cylinder heads.
What casting number?
A guess as to year of vehicle they came off of?

They are not Magnum R/T heads, correct?

For a period the MP catalog listed ported Magnum heads for sale.
Perhaps someone here on Moparts would know who did the actual porting for MP ?
Mike Leach did Tri-Y Magnum tube headers, did his shop also do the ported Magnum cylinder heads?

I think one can state with confidence that these cylinder heads were designed with a top priority to reduce NOx pollution using the concept of Fast Burn.

But the cylinder head design was not enough alone for NOx.
EGR still had to be used from 40% throttle opening to 60%.
In those years, once past 60% throttle opening,
the “Rep. John Dingle Jr. Passing Power legal exception” kicked in
and emissions did not have to met at all.

My gut tells me to bet that
a MPI intake manifold combined with untouched R/T cylinder heads and cam
will out do any home porting job.

But if it is fun by all means do it.