ignition resistor question

The problem here is that you could be ADDING problems by doing this conversion on a truck you cannot get to run

What could be the problem now?

Lots of things

The distributor could be bad. Pull the cap and inspect the pickup coil and reluctor for rust, debri, impact damage and wiggle the shaft, looking for excessive wear. The gap is to be set with a brass feeler (available at O'Reallys) at .008" That's inches, not metric

Even if / when you convert to HEI you'll need a working distributor

Hook the two distributor terminals to your multimeter set on low AC --that's right AC volts. Crank the engine, it should produce about 1V AC

Remove the ECU box scrape the mounting ears and firewall CLEAN and remount with star lock washers. The box MUST MUST be grounded. 14 years of rust..........................

Inspect the cap and rotor for moisture, dirt, grease, carbon tracking, spark punch through on the rotor. Do NOT check spark using the factory coil wire. Rather, hold a grounded probe, or "rig" a test gap, right at the coil itself.

Temporarily jumper a clip lead from a battery source (the starter relay battery stud) over to the coil + terminal. Don't leave this hooked longer than necessary to test.

"Wiggle" all connectors. Remove the distributor, ballast, and ECU connectors, and 'work' them in/out several times to scrub the terminals and 'feel' for tightness

Pull the distributor connector. Use a grounded clip lead. With the key in 'run' ground first one then the other of the distributor connector on the ignition harness end. One of the two should produce one spark each time.

Is the ECU wet / muddy/ dirty? That big transistor and heat sink is HOT above ground, with "high voltage" from the coil primary. IT WILL SHORT if it's wet and dirty and missfire and quit.