340 Hydraulic lock inspection update...

I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?