If you're gonna take it apart that far you should, at a minimum, ball hone and re-ring it, assuming it has straight bores. You can take the block to a machine shop and ask them to measure the bores with a dialbore gauge and a mic. Especially check the cylinder with low compression. Also, it seems like you are not sure where each valve came from cylinder-wise. You need to keep track of each part you remove, either so you can accurately determine what's wrong, or to ensure they go back in the same place they came from (if you're going to re-use them). Also, mark them for orientaion, ( front-rear, top-bottom) and make sure they go back the same way they came out.
