Last minute Sunday prep for a toys for tots cruise tomorrow.

My brothers Charger has a new electronic conversion harness. He bought the correct electronic voltage regular(small blue style) and it was defective.
We have tried the point style voltage regulator with no luck. Works for a while and then no good.

Here is the question. Can I cut the voltage reg. connection off an old 70 up style harness and make the 70 and up style voltage regulator work on his car. I am guessing I may need a dual field alternator. If so can I run the second field to the ballast resistor and be OK. Has anyone tried this. His harnesses are all new and I do not want to fry them. I know we should wait for Tuesday and get the right parts but we are just trying to find a way to get it to the show. Thank you for any help and or advise.
Reid