IF (and I say if) someone has replaced the fuse link with a 30A fuse, that is nowhere near large enough.
Start by going there and downloading the 72 shop manual for free (Thanks to AbodyJoe)
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
There's some more good info and additional manuals here
http://www.mymopar.com/index.php?pid=31
Unrelated to your question, but wander around in there for awhile, as well as the Master Tech Service Conference stuff
Last and possibly most important, read this article
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
which came from here
http://www.madelectrical.com/electrical-tech.shtml
Even if you do not do the ammeter bypass as in that article, it points out the pitfalls of these old girls. Most any connector is suspect, as well as switches themselves. In some cases the ammeter itself can give trouble.
