Hi Bob, I can vouch for the antenna problems! I just bought my 9,000 mi original TTA with a bad antenna. I finally located an NOS one but haven't put it in yet. It doesn't appear to be a fun job.
Anyway I can tell you that from looking at the NOS one, there is a plug on a 2 foot pigtail connected to the antenna. I'm not yet sure if this plug goes thru the firewall or if it stays in the inner fender! If you can get at the pig tail and find the hot wire you can splice in a switch. I will probably do this to preserve the new one.
The previous owner pulled the fuse to keep the motor from running but this also disables about a dozen other controlls including the horn, door locks, power mirrors and more!
I'm hoping to be able to do the replacement just by taking the plastic inner fender off. I really don't want to loosen the fender!
I'm sorry this wasn't much help but I'll give you the details once I get into the project.
Later, Vic
BTW, If you don't need that "old engine" anymore I'll gladly take it off your hands!!! LOL