...I'd first remove Tstat and run it without and see if it still overheats...I've also noticed that the Head to Block Coolant passage hole in the El-Ring brand Headgaskets (for cyl no 4) often doesn't line up perfectly...I usually simply make an adjustment cut in the gasket so there is less restriction...but I would NOT expect this alone could cause overheating.

Overheating is more likely caused by something in the Head, like Tstat, or Pump (I realize Pump is not in the head, but I associate it more with Head than Block).

...or Distribution Pipe...do you know of what Eric is talking when he speaks of that?...it's a Brass Pipe running from front of Head to rear directing Coolant from Pump to combustion chambers...Pipe has distribution slots at each cylinder which need to be clear to deliver Coolant.

Good Hunting!