I'm going to assume you already have a rollbar and skip that discussion.
I would definitely run with anti-submarine belts, either a 5 or 6-point. When I had my Sprint, I used a 6-point setup. I did not have a submarine belt hole, so I anchored the sub belts to the seat mounting structure and ran the belts up through the side belt holes. You sit on the belts and then draw them up over your groin, like a rapelling harness. This is an approved mounting configuration, or at least it was several years ago.