I would pull out any harness that you did not replace (dash harness?) Carefully untape it, and look for any wires burned together. IF you are careful, and tie the branches off and work slowly, you can do this, just lay it out on a bench where you can deal with it.
Also, for troubleshooting like this, "rig" yourself a couple--three different test lamps. The idea is you want to SOMETIMES be able to LOAD a circuit more than a typical test light
I have a typical store bought TEST LIGHT
I use a STOP/ TAIL socket, and can use it in 4 combinations:
1 tail lamp, light load
2 stop light, heavier load
3 tie both together, really heavy
4 leave the ground "float" and hook the circuit to the two wire connections, leaving the filaments in series for a REALLY LIGHT load
HEADLIGHT. If you have an old headlight, these can be really handy
SHORT FINDER, like the one KD makes
[ame="http://www.amazon.com/KD-Tools-2524-Circuit-Detector/dp/B000RH6JP6/ref=pd_sxp_f_pt"]Amazon.com: KD Tools 2524 Short Circuit Detector: Home Improvement[/ame]
ANY of these above devices can be wired in series with the battery ground. This will prevent harness damage while you are troubleshooting. If you use a HEAVY load such as a headlamp, this will allow enough current to flow to check such things as the interior light circuit and get a low glow out of the parking lights, etc, but will PROTECT against harness "smoke."
The KD (and others) short finder works like a circuit breaker. You put it in series with the battery ground, and a short causes it to recycle, like signal flasher. The "meter" helps you find the short location by changes in the magnetic field around the short.
There is NO way around it. If you are serious about driving and maintaining one of these old girls, you MUST get yourself a reprint of the FACTORY manual, either on CD or paper. You can download some here for free, but nothing there has 71 wiring. You can download the 72 manual, which is complete and may be close enough, wiring wise:
If you decide to download some of this stuff, some links at the top of the thread are broken, but have been fixed later on, so scroll down
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download
The 72 manual:
http://www.abodyjoe.com/pictures/Misc. car info/1972 Plymouth Chassis Serv Man.pdf
Closest thing I have is my old 70 manual, and can post scans of that wiring.
You may be misreading the wiring, or the new harness may use different color. Originally, BLACK is the alternator output, VIOLET is involved with headlight wiring
The 72 diagram shows the fuse link comes out as dark blue but connects to red, onward to the start relay. That could be confused with purple.