Well, over the years, I did the same darned thing wi9th Jag Mk 1 and Mk 11 (two) sedans and MGA's owned every MGA there was EXCEPT a Mk 11 (two) delux roadster and cpe. Bought a MGA 1600 that had at one time a Paxton supercharger on it. The bearings had been blown out and the old gal had only 10 psi at idle . Sold it as it was, and the new owner had to replace the bearings. TOO much stress on the bottom end. Competition MGB's cannot stand "high" RPM's and "high" compression, either. Typically they would use the overdrive rear end ( Norman de Laycock electric I think) it would stop working and the carburated engine would go BANG and not run anymore...
If I was going supercharged MGB I'd go MINIMUM to competition springs. I'd add an electronic distributor with a built in rev limiter at, say, 6600, 6700 rpm's. Were I doing it from scratch, I'd use a 1967 engine, disassemble it, machine it , block and head, flat, use new no lead gas insert valve seats, valves to match, a little higher lift cam, match head ports and manifolds (new steel exhaust header) , generally clean everything onside up, and use the lowest numerical rear end gears available.
Try Moss Motors in CA, and, of course, the Advertizers in the SCCA 's monthly mag. for a source of parts that might save you a catastrophic failure in the future, and that's a real paim,,,btdt.