Welcome, you have come to the right place to learn about the Norton world. Based on what you wrote I'm immediately skeptical. The seller's claims make the Norton sound more like a hand grenade then a motorcycle.
Whether or not it left the factory as a Combat would be revealed by the engine number, which, hopefully, matches the frame and transmission numbers, worth a check not that a bitsa bike belongs in a leper colony, but some title states get upset if the number don't match.
.060 overbore? I was faced with this prospect on a 750; more learned members of this forum pointed out that taking a 750 to .060 over requires a sleeve, which, because of its' size, can be seen from between the fins, not good.
Paxton Ignition? Probably not especially if the Norton in question utilizes a, as manufactured, positive (+) ground electrical strategy. I think of Paxton ignition in association with V-8 muscle cars, no reason you couldn't adapt one to a Norton, assuming it is compatible, but why? There are many electronic ignitions that are made exclusively for Norton applications and they are less expensive (new) than a Paxton unit. I could see some rational for using a Paxton, if it increased the power of the spark, but they are timing controllers.
11:1 CR? That is really pushing your luck, even with a cam as aggressive as the 4S; probably OK if you run on race fuel, and not when the ambient temp is above mid 80s, and you don't get stuck in traffic.
A single 34mm Mikuni? With that cam and that CR you'd want twin monster carbs, the Norton you are looking at is analogous to putting a pair of outboard engines on the Queen Mary. A pair of 34s is more like it although with the available manifolds for adapting same there is no room for your knees.
I hope I'm wrong, but it sure sounds like the seller is more comfortable selling Chevy's and Fords to high school drop-outs. Run, don't walk away from this deal, or get it for $1500 or less and plan to spend a bundle defusing the grenade engine (and every other thing that has been touched by the person who thought that Paxton was neat).
I feel bad raining on your parade, having a Norton is a wonderful pursuit. The example you are looking at may well be worth buying, depending on price, and what you are capable of doing, but it doesn't strike me as a daily driver, but rater a daily project.