Welder,using a scanner find out what codes are in memory. write them down and keep them. Erase PCM codes and repeat previous step. See what returns. There is plenty to speculate but you will surely run out of money before you run out of parts to change. Autozone will read the codes for free. you need to decide which direction to follow,Fuel or Electronics.Pay a reputable shop for an hour of diagnostic time. Measurement of fuel pressure is a must. Before you cut off the CAT, removing one of the O2 sensors or simply loosening up the exhaust piping will get you the same diagnostic results,which is do Have more than one inch of back-pressure. Re-racking electrical connectors and cleaning grounds is a simple/easy way to eliminate electrical. Placing a vacuum gage on the intake manifold and interpret the readings will tell you how the engine is breathing.or if there are timing issues related to mechanical problems. A Haynes manual is a economic way to understand what it is your dealing with. Hope this helps! Get back to us with some results and we will give you guidance thanks, Mongoman
1973 W-100 O/H 360' engine, w/a Edelbrock :1406 carb,2176 intake manifold, 2177 performer cam/ lift kit, Lokar cables, Dana 44 front axle ,A-727 auto-trans.Np-205 trans-case, Chrysler 8 3/4"SF rear axle ,All drum Brakes. Classic Auto Air-conditioner package.