to-20 no compression

I had an engine one time where the key in the crankshaft gear broke, the crank gear would slip on the crankshaft and throw the timing out. Took me a loooong time to figure that one out.

I hope turning the engine by hand, and watching the valve and piston action help you figure out the problem. If pushrods are bent, probably need to pull the head and check the valves and pistons real good. I have seen dropped valves punch holes right thru those aluminum pistons.
Hopefully it is something fairly simple, and fairly cheap to fix.

2. Did you use a new head gasket? Is the head torqued properly?

3. When you had the head off, did you check the valves and pistons for signs of damage (after the incident with bad cam timing)?

Since you had compression on 2 & 3 (was it good, or weak?), here is what I would try next:

Remove the valve cover and spark plugs. Put a large wrench on the crankshaft nut. Turn the engine very slowly and watch the action of the valves (all you can see is rocker arms, valve stems, and push rod). Starting at #1 cylinder, make sure all of the valves are being opened correctly. This is the order of opening for 2 revolutions of the crank:

#1 Int and #3 Exh
#3 Int and #4 Exh
#4 Int and #2 Exh
#2 Int and #1 Exh If it becomes more difficult to turn the crank, note which valves are being opened/closed. Check that the valves close fully after being opened. Check the valve lash (.014 Hot). It should be apparent if you have valves stuck open, especially on #1 and #4. If you find valve problems, you need to rebuild the valve train/head.