First Check all your fuses...
Look for those marked ECM, ECU, Computer, INJ, AND also check the fuses like RDO, and the like..
Don't just eyeball them, test them with a continuity tester to be sure they are not open..an open can occur at a "Leg" of the fuse you can't see and it will look perfectly fine...TEST them ALL.
Check the Tie point on the battery power junction , where the fuse links are located..(on a Chevy it's on the solenoid big bolt or the horn relay , or even at the battery itself..) On A Dodge I couldn't say..
Be sure all firewall plugs and harness are tight and properly seated...and have no burned or bent or corroded pins .
Backtrack WHERE you welded..and inspect. I had a Muffler shop WELD my computer harness to an exhaust flange on a Corvette, and ace the system..(The Dummies..._)
Lastly, If you DID a lot of welding on the Frame or pipes, and Did not remove the computer, It is possible you did destroy the computer, with a frequency welder..ALWAYS to be safe remove the box before welding..better safe than sorry..BUT I don't see that as Cutting power to the Coil...that is separate.
Check your ENGINE STOP relay, this cuts power to the coil and fuel pump, (if electric) and is most likely the problem..Especially if the relays were swapped around..be sure it is in place and working. If need be, buy one new relay, and swap it one at a time..and see if spark returns.