1974 D300 360 fresh rebuild will not start

67Dart273 said
This nonsense of cam timing is stupid.

I disagree, this is what makes the most sense with the information provided.

67Dart273 said
the valves may be open at wrong time or "just open."

Enlighten us, how dose that happen without fouled up cam timing?

67Dart273 said
And you cam time them EITHER at "6 and 12" or at "12 and 12". When you rotate the crank one turn, the marks will be the opposite location of where they were at first.

Yes the CAM can be at 6 or 12, but if the crank is timed at 6 then the cam will always be 90 degrees off (1/2 a crank stroke) and his compression when from 120 to 60 (about 1/2).

No one is saying that this IS the problem but based on the data I think its a very viable place to check.