Congrads on becoming the proud owner of a classic, and welcome to the forum.
There could be many things that are causing your battery to discharge, including the fact that it might not be charging at all. You could have a bad battery (even new ones are sometimes bad), same for the new alternator (these things are known to eat alternators, have yours checked), a bad isolater, improper hookup., bad grounds, dirty connectors or terminals, a paracitic draw somewhere, loose belts, and a number of other things. It is really hard to determine what your problem is with out more information. How long until the battery is discharged? Have you fully charged the battery first? Pictures would be nice.
Also, there are a number of threads here in the forum dealing with just what you are experiencing. Do a search on "alternator" or "charging system". There is even one about that red wire you are talking about if memory serves me right.
I am by far no expert on this topic, but I have had the same problem at one time or another. There are many really bright and talented folks on this forum, and I am sure that one of them will be able to help you. But do some poking around in here and some inside your MoHo and come back with more insight, it would really help.
Today being Saturday, many folks are out camping and might not see your post for a while. Just keep at it and let us know what you find.