I had a drive in a new RV8 when I had my BGTV8. It was OK I suppose. The seats put you high in the car. The interior was amazing new, but they don't arf get tatty with age. I still look at RV8s occasionally , but from my perspective, my Roadster is so far ahead in every way that I doubt an RV8 would do the business. A bespoke V8 conversion in a new shell would be the way to do it, but then the Duratec family of engines would give the same or more power and a better balanced car.
Tha Mazda running gear in the Frontline MGBs is a good match, but they are far too expensive for a jazzed up MG.