The person or persons that suggested to check the wiring were right.
I would start with the grounds don't over look the ground at the starter and if you have not already done the DR Lee fix do so.
You might have to remove the starter to get to that connection.
Next I had a flixering problem that would come and go and I fixed that by replacing the alternator.
I bought mine from NAPA that is rated at 120 amps.
That starter really spins with that much amps.
Hope this helps.
Late 96 C2500 HO with factory 97 upgrades.<p>4:10 locker