Does this 5.9 Magnum look ok?
I made the mistake of not tearing down a used 5.9 Magnum short block that I was not able to get a compression test on, as it was essentially a core motor. I resealed, recammed and replaced the timing chain set.
It ended up with only 90 psi cranking compression in the #2 cylinder. The motor ran well enough, but it smoked on deceleration and used oil.
If I had it to do again, I would have had the block boiled out, honed it and replaced the rings and bearings. That's assuming your pistons are still serviceable.
Toss the heads and get some of the inexpensive replacement heads that are readily available. You said this is for a '91? That's OBD1 stuff. I wouldn't waste the time on that. There's really no way to tune them to take advantage of the cam and head change.
If this is just for a daily driver, it sounds like you would be better off just getting a known good running engine, reseal it and stuff it in there.