Coolant leaks at the back, upper and lower corners of the heads is very common. The larger water port from block to head is at the rear of the #7 and #8 cylinders. There is only a vent hole on the front of the heads.
130 psi is alittle low, should be 150-165 on fresh rings and newly lapped valves. I strongly disagree with whomever said not to plane the heads when you have them off. If they have never been off the engine, they are sure to have slight warpage. We're not talking huge, but runout of .0015 is enough to cause it to blow once reinstalled on a new, composite gasket. Have them sent out to any GOOD automotive machine shop. Instruct them to "Plane to true". this is a minimal cut. While the heads are off, pull all the vavles, keeping them, and the springs, in order. Lap them with fine lapping compound. You don't need any fancy equipment. Lightly smear the valve face, drop the valve back in, and hand chuck your cordless drill on the stem and spin with light pressure, moveing the valve on and off the face. Clean all lapping compound well before reassembly. Replace the stem seals.
When you get the heads off, check for any sharp ridges on the cylinder wall, about 1/4" down from the top of the joint face. If it's severe, it will be a possible source of your low compression. Also, if it's severe, check the bore for ovality ( not the rich chocolate breakfast drink; as in 'out of round')
FWIW Liners in LR (or any of the GM, Buick blocks) do not 'drop'. They can't, as they bottom out on a counterbored step. They become loosened when the engine is severely overheated, and can move up, the thickness of the head gasket.
As Okie said, you can do this job in the car. Getting at all the bellhousing bolts is a major pain, unless you have a sixpack of midgets on the payroll.
PS: Lifters aren't that expensive. And they will be worn. So too will your cam, but that's a step beyond.
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