Cracked block, huh... what else is the engine doing....like loss of power? weird noises? etc. Run a compression check across all 6 and check the carb. Too lean of a mix can make an engine run hotter...so I have been told by several mechanics. You can also remove the radiator cap when the engine is cold, start/run it and as the thermostate opens, observe the water flow rate. Also check the timming. and advance.
1975 CJ-6 1983 CJ-8
1986 CJ-7 Laredo 1986 TJ-7 Trail Jeep
2003 Inca Gold TJ Rubicon