Lets build a CHEAP(!!!!!!!) bracket motor!

YY1 said
Very, VERY common to find cross hatching still in 150,000 mile Magnum bores.

That strongly suggests they don't need re-ringed, bored out, etc and can be run as is.
A more common issue is rod bearing knock.

I'd keep the Magnum exhaust manifolds as they flow great (esp the 1992 ones) and sound great, plus you shouldn't have steering or ground clearance issues like you will with $150 headers (plus you save the $150)

Dany's Magnum had 200K with crosshatch still visible.
We did NOT ring it,and with thin head gaskets and EQ318B's it had 5% leakage.
Even on the cyl with a new standard piston and the used rings off the old piston on it!!!