Nothing wrong with the Delco - I'd take a CS or SI series over an ND any day of the week!
However, it should be noted that "relieving" the PCM of the job of regulating the alternator's output will throw a persistent code and CEL/MIL (something like "Generator Field Not Switching," usually) and this will cause you to fail periodic inspections, if you are subject to such. It can also mask other faults - therefore, I wouldn't suggest doing it unless you had relatively unfettered access to a "code reader" - and used it every month or two, to see if there are any other codes hiding behind the one you always have.
This also applies if you use an ND alternator - but wire in a separate voltage regulator instead of using the PCM regulator circuit. Forewarned is forearmed.
RENIX doesn't care - if you use an externally-regulated alternator with an external regulator, so what? That doesn't pose a problem for RENIX controls. Therefore, you could adapt the mounting to accept an ND and use, say, a Prestolite external marine voltage regulator - but you'll still have to modify wiring, and I don't consider the ND to be as durable as the Delco (I've got experience with both in industrial applications - which is about as harsh of a "regular use" environment as you can get...)
Have a Delco "upwound" by a competent shop poses no particular trouble, you can even get kits of internals to do it yourself if you like. I leave that up to you (with the caveats explained above.)