The inside of the heads look fairly clean. That may well be a good sign the engine has good life left in it.
Were you given any history on why it was parked? Maybe, as was suggested, it was over revved. If that is the case you might be lucky enough to get away with replacing push rods. You are going to need push rods no matter what. If you want to take the minimalist approach get some new/used push rods, drop them in, put the rocker shafts back in, check the engine timing by turning it by hand and make sure it doesn’t meet interference. If it doesn’t meet interference and the engine timing seems correct, do a compression test. If it improves at all, see how it runs.
If it meets interference when turning by hand and or the engine timing is off, (or if you don’t want to be a minimalist) pull the heads and timing cover and do full inspection.
My rule of thumb is always take the minimalist approach assuming the best and work from there.
If you want to spend as little as possible during diagnosis, I might have some used push rods I can send your way.
EDIT - I somehow missed you had zero compression on 2 cylinders. Im sure you have the same thought but I suspect you have bent valves. Check the compression with the push rods out. I really doubt it will be better. You don’t even need to put a gauge on it. Just rotate it by hand to see if it has any compression. Ive replaced individual valves on heads and put the heads right back on after correcting what caused them to bend with good success. Make sure the heads are flat off course.
