440 wont start

'T fact is, it just doesn't take all that long to CHECK

CHECK the valve clearance. If you have hydraulic tappets, the pushrods should at least be rotatable with valves closed. Any chance the stem height is too tall on those new heads?

FORGET you "think" the timing is OK, CHECK it.

Pull no1 plug, stick your finger in the hole, bump for start of compression. Bump around until marks are 10-15 BTC, look where the rotor is, and make sure no1 wire starts there. Maybe you were asleep. Did you run the wires the correct way? CCW for B/ RB, and CW for SB engines.