I would strongly recommend using 91 in your SC based on what I see with these engines over the long term. For sure, its cheaper than new P/C's.
Set the timing to factory specs and you'll be OK.
Unless you have the resources to buy, install and tune something like the J&S Knock Detection system, you'll be better served by dealing with any detonation proactively by using good gasolines.
(Your RV sounds fun as those are made a few miles away)