Water in the crankcase leads to rusted gears and both sides of the cylinder walls. It took sledge hammer and two crowbars to get my junker engine apart (after two weeks penetrant soak). At least it was instructional.
Rings on these seldom go that bad and heads are easy rebuilt. The other motor looks like your runner with this one a parts supply.
BTW, inspect the frame cross-member where the center stand mounts. They tend to collect water and rust out. Mostly important for the center stand, but that stand is very useful on such a heavy bike. In '79 they gusseted that cross-member.
"Love 'em all.... let God sort 'em out!"
1978 GL1000 - winter project for 2020 challenge
2006 GL1800 - the Black Pearl
1979 GL1000 project - to be restored
1978 GL1000 with '75 engine - the Hunley
Ex '79 CB750F rat bike - the Rocket - SOLD!
Ex '86 SEi
Ex '77 GL1000
Ex '75 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped