The main difference between the Renix and HO engine (apart from electronics) is in the head. The HO has straighter intake runners, a slightly higher intake entry level, and flows a little better as a result. Therefore, it is possible to "create" a HO engine using the Renix block and staying with the - very solid - OEMR Renix electronics and saving yourself a batch of work.
Therefore, why not rebuild the lower half of the engine (it's pretty much the same anyhow - just has an extra sensor or two and not much else) and get an HO head and manifolds? The Renix TB can be adapted to the HO intake, and the exhaust is otherwise the same with the exception of there being no EGR valve (the cam grind was changed in 1991 to delete the EGR, and probably runs better as a result. The new cam will fit the Renix block - all the modern AMC cams fit the same bosses and bores.)
Also, if you have anything specific in mind, you might want to explore some other avenues while you have the engine torn to bits. I'd be happy to help, but something more than "just more power" is needed to answer that question...
5-90