Hey how are you
1-We need fuel & spark to start , on this truck The distributor is #1 issue on them fort this intermittent condition
but you have replaced that already for the spark condition
2-the fuel pump pressure specs on this truck is :
1990 Dodge or Ram Truck
Fuel Pump Pressure ......................................... 14.5 psi. (100 kPa)
Fuel Pump : The fuel pump mounts inside the fuel tank, from the top of the tank. The fuel tank must be lowered to access the fuel pump.
3- The Engine control module : The engine controller is located at the front left-hand corner of the engine compartment, behind the headlight assembly.
you need to take the electrical connector and inspect for broke pins making intermittent connection ,get electrical contact cleaner and spray connection and retest
4- the key is to check at time of no start , is to check what are you losing fuel or spark or both at that time ?
5- when it does not start ,get a starting fluid can and spray in the intake ,does it start ,if it does we know it fuel issue
6- please click on blue link to view the fuel pump & pcm location
7- so most common issue ,for intermittent no start the disturber (You replaced already) , fuel pressure & pcm or pcm wiring
Please let me know if you need anything else on it
ASE Certified Technician