Backfire turned bad day

OP, what ignition system and rev limiter do you have? Has it ever backfired before at the limiter? Some limiters act by randomly cutting out firing cylinders and will build up unburned fuel in the exhaust that often gets lit off. (Hence the popping.... ) It almost sounds like the ignition and limiter failed when it went into rev limit mode this time.

What is different between the driver's and passenger side? The compression readings are around 25 psi different between the 2 sides; that normally indicates a compression ratio difference of over 1 point, which is a lot. Did you take the compression readings with the carb in place and the throttle closed? While you have the heads off, it would be good to measure the piston's deck height on both sides to see if they are maybe .010"-.020" different.

You can do a spark check with the heads off. Put the distributor back in and hook all the ignition up. Take the spark wire from the coil and place it so the distributor end of that wire is about 1/4" to 3/8" from metal, crank the engine, and see if it jumps a good blue spark over that wide gap in open air. (BTW, it is NOT a good test to look for spark across a spark plug gap in open air. That small gap can be jumped in open air by a 5000V spark, but 25000v or more is needed to jump that same small gap in a compressed fuel/air mixture.)