[HO455]

This link describes how those full load style amp meters work and why they can be a problem. The article refers to Dodge trucks but theory is the same. (GM discontinued that style amp meters in the early 60's) Unfortunately for you unless you pull all of the wire loom tape apart and verify what was done you may be driving on a time bomb of sorts.
I believe Rustypile is correct in that you should be able to remove the old amp meter and connect the 2 leads together and everything should work. I however wouldn't be able to stop wondering if everything the PO did was copacetic and never going to fail. Just my opinion.

http://www.madelectrical.com/electri...p-gauges.shtml

Here is a second link about Chevy wiring. The article is based on earlier car wiring and the actual wiring in our trucks is somewhat different. Like the horn relay is under the dash and not tied in directly to the main charge circuit. But it is close enough if you compare the article with our wiring diagram it will make sense.

http://www.madelectrical.com/electri...evymain1.shtml