No Start

I have a 1990 GMC 1500 pickup with a 5.7 with about 100,000 miles.
This truck has been running perfect until my son took it off roading and the engine died and would crank fine but not start.
I have since replaced the distributor, cap, rotor, plug wires & plugs, had the ignition module tested (tested fine) and have replaced timing chain & gears.
There is fire to the plugs and I can see fuel being sprayed into the throttle body as the engine is being cranked over. I have made sure #1 cylinder is on compression stroke with #1 plug wire on distributor cap is pointed at by rotor. Makes no difference when distributor is turned either direction except engine will kick back when timing is advanced too far. No back fire either.
Engine cranks fine but will not start.