Which head gasket?

I have a bad head gasket - at the very least. The telltale signs are there - residue in overflow bottle, pressure through the bottle, rough idling, etc. My question - can I isolate which head gasket might be bad? I don't want to do the rear if the front is only bad. The rotating of the engine and removal of lower manifold on the rear doesn't appeal to me at all. I could pull the plugs and vacuum any water in the cylinder if the water crossed over to the cylinders. But what else might isolate a bad gasket from a good one? Thanks

You could pressurize the front cylinders with a leak down tester, at least you would know if it is that one, but they really should both be done. Air pressure would not hold at all in the suspect cylinder,

Do not only replace one side, as increased cylinder sealing on the front cylinders will lead to failure of the rear. If you're going to tear the motor down, do both and save yourself from doing it again. It's more labor, but only one more $15 gasket to do both. IF you only do one, and then the other bank fails, you will need about $150 worth of gaskets to reach that $15 gasket doing it the second time.

Do both sides,do it right the first time.Also get the heads checked for warpness;.If warped,get them milled and take off brackets,sparkplugs,etc off before taking to an auto machine shop.The headgaskets will not seal very well with warped heads.