Possible blown head gasket or worse

How's it goin! Helping out a friend of mine with his car, it's his first old car and doesnt know much about mechanical work.

For starters he has a huuuge vacuum leak. (He tried to install a new intake and four barrel carb on his own). His water pump went bad and began to leak around the pulley area and he did not fix it and he continued to drive his car all over town. He would refill it but nonetheless that thing was broken and leaking bad. Also has a huge exhaust leak... After the intake swap he did not go to headers or get a blocking plate for the exhaust manifold, so that thing is open and ticking like crazy when it's on.

What happened and why I feel it's a blown head gasket.

He got stranded at autozone when his throttle cable snapped. He called me an I went over there and had him purchase a universal throttle cable. Got that hooked up and I corrected the way the carb was hooked up. He had the throttle cable hooked up to the choke. So it would open and close the butterfly valve when he would press the gas pedal, I have no idea how this thing was even drive able when I saw that haha

So I told him to crank his car on. It wasn't cranking right. It would do like quarter cranks, with the starter knocking every couple seconds. Just a huge loud horrible mess. Then if you hold it the engine stops cranking but you can hear the starter still spinning.

If you do this enough times it will eventually start to crank but it acts as if it's not getting any spark. Then it will finally turn on but idles horrible. Needs a high idle to stay on, and when you drop it in drive it will rumble like crazy and again, want to turn off. Can't really get it past 30mph without crap getting really bad. So I have it at my house right now and I pulled the plugs to check them out. First 3 or 4 look as if that may be where the gasket leaked. Then 5 and 6 are oil/gas fouled I believe. Gonna run a compression test before I pull the head, just to give me somewhat of an idea of what could be going on.

What I think happened...
Vacuum leak and incorrectly set up carb= poor running condition
Exhaust leak-maybe could have affected the valves??
Bad water pump-culprit of issue. The car was run with a bad water pump/leaking. Ran the engine dry had no idea it was heating up and blew a head gasket.
Bad crank-water in the cylinders, not letting the engine crank right until it's pushed out enough water, then once you've dumped enough fuel it will finally ignite and let the engine run. Of course the blown head gasket is causing the improper running.

My plan is to run a compression check, pull the head, check it out, get the head inspected at the machine shop and redone according to what they feel (I got a good machinist). Check out the piston tops and cylinder bores. Of course drain the oil pan and look for water which I bet there is, hopefully not any metal shavings. Slap it all back together if all is well, put the water pump back on and make sure timing is correct.

I decided to post on this because I just want to get a second opinion on what somebody thinks could be the issue? I feel like it's a blown head gasket maybe worse...

Slant six duster, I believe it's the 225. 904 column shift. Electronic ignition. Recent tune up.