Based on your first few sentences, my guess is you messed up your firing order with the new cap and wires.

Second guess is another wire near the dist cap got pinched or is shorting out and some wiring got fried.

What was the neg battery terminal arcing on??

Sorry, negative on the battery was smoking and throwing sparks. Now I have replaced cap, rotor, wires, plugs x2 and the fuel filter. Still no start. Anybody know where I can connect a fuel pressure tester to? 1996 502 mag mpi

There is a schrader valve in front center of intake, kind of tucked under front of intake.

yeah this thing has me at a loss. It has fuel, spark and compression. Fuel pressure is at 38psi when the pump primes. All cylinders are at 120psi.

It doesn't have spark, if it did there would at least have a backfire

Just rebuilt a 454 MPI and motor was running fine when removed. Tried to start on pallet and no start. Replaced the EST module and it fired right up. Why that happened we have no idea but that's what it was

If you have fuel,spark,and compression it should run. Only stipulation is that ignition occurs close to the correct time. Pull a plug and see if it has fuel on it. Just because you have fuel pressure doesn’t guarantee injectors are firing. How did you check for spark? At the coil or at the plug? Make sure firing order is correct on the cap and follow wires down to plugs. Make sure you used correct rotation when checking firing order.

Have you hooked it up to a computer to check if it is throwing and codes? That would be my first starting point.

If that is the case, there is a good chance you could have fried a bunch of wires and maybe even the battery or ECM.
If the neg cable is getting hot and smoking/sparking, it is not connected well and not grounded properly.