wait.... do what with the cam because what about Air police?
In 1987, when the thing came out, it was saddled with a (wholly unnecessary) EGR system.
For 1991, when ChryCo took over design work, the EGR system was (properly) eliminated. It isn't necessary on low-compression engines, and I've got reports that say it runs cleaner without the thing than with (not my test - CA Air Police tests. The
only point of mechanical failure was the EGR valve, and emissions were damned near zero.)
Quite a few people think it was due to changes in the camshaft profile (done to promote exhaust gas reversion, thereby accomplishing what the EGR did,) but there wasn't any change in the cam until 1995/1996 - when OBD-II hit. There were slight changes to duration (and, I believe, overlap) at that point.
If you're subject to the Air Police, swap out the short block, put the 2000 cam in the RENIX SB, and install new lifters. That will give the same cam profile (which is ground to get along with OBD-II controls.) I do not believe that the OBD-II cam was much different from the RENIX grind, so you may not even get a CEL/MIL from having the "wrong cam" in there - OBD-II can sometimes tell when the cam is wrong for the design, and that's what gives OBD-II aftermarket cam designers fits (and why so many cams say "Not for use on Computer-controlled vehicles" or "Not for use on Emissions-Controlled vehicles.")
That's what I was trying to say. Putting the RENIX short block under the OBD-II top end should allow you to do the swap with minimal work - since all of your trouble seems to be in the short block anyhow, and it would save you the trouble of adapting the OBD-II stuff to the RENIX head and/or manifolds. Problem solved!