Engine Stamp Pad Questions

Looking to buy a 383 from a friend, cast in 1970, appears to be a stock 4 barrel, crank drilled for 4 speed with correct early bushing. It s/b 8.5:1 compression.

On the pad below the distributor is:
G383, assembled in 1971, 383.
Next is assembly date, don't recall what it was, I'm dumb and didn't take a pic.
There is a maltese cross, my understanding is .001" undersize main bearing journals.

There is also HP for High Performance.
I don't recall anything else at the moment.

I've read many posts where people state 2 barrel 71 383s got a cast crank, Allpar states: "In 1971, the year also saw the use of a cast iron 383 crankshaft as a cost saving measure, on automatic-transmission cars." No mention of carb.

Can anyone explain exactly what was different on an HP engine?

What is the purpose of undersize main bearing journals?

I know pulling the pan and looking at the crank will solve the cast or forged question, but is Allpar correct?

I don't believe the 8.5:1 comp is a deal breaker, just looking for a good engine, but what would it take to raise comp to the 1970 spec of 9.5:1?