Hi all I am new to the forums, great place by the way, and I have a question to ask. I need some opinions on some compression readings on my car so I can know where to go next. Let me give y'all the whole situation. I came down for christmas from college and I was driving my Z.... One day while running... and not very hard... it starts missing. I take off the valve cover to find one of my rocker arms laying besides its respective post. I immediately had a heart attack but the engine was fine, after putting the arm back on and adjusting the whole set of valves the car ran like a champ. After that spill about two days later I was pulling off the head to replace it with another I had laying around that I knew was good (it was taken off due to the nature it was getting a little worn and I bought rebuilt one off of ebay). So I swap all the parts and cam and keep all the springs and arms matched to where they were on the other head. The car runs for about a week then one day I am turning a corner it blows a ton of black smoke and loses power. I get it back home and it sits for about a three months until this weekend when I am home long enough to work on it. First rattle out of the box I run a compression test and get the numbers in order from cylinder 1-6.
120 130 90 90 150 140

Bad times no doubt, so I go on ahead and start the oil in the cylinder while testing trick to see if it was the rings or my head that went bad.The numbers read as follows

150 180 130 190 150 160

There is only one problem here... I forgot to put oil in the fourth cylinder (the one that jumped 100 psi). I did not do the oil test to the fourth cylinder due to the fact it read in the range I expected. Now I do not know whether to think I need a new bottom or top end, being a college kid I have to choose one or the other pretty much my dad can't help he is paying for my mom's chemo, so I am asking for anyone who has an idea to post it, I miss my Z I haven't gotten a good drive in it for months now

Mechanically and Electronically it is in perfect time with a brand new crane xr-3000 ignition and now an accel coil my brother gave to me since my ps-91 fireball went bad If you have any other questions just post them I am sure I forgot to mention something here.

P.S.
It is a F54 block with a N47 head on it, yes I lapped the valves in my self but I have done it many times before... raced a formula one to get that experience... 8 grand bad for z.... anyways I am pretty good at putting these together if they are in decent shape so no worries there.
By the way.... sorry for the novel