Thanks, Joel. I found the horn. I'm in the process of testing other electrical items (e.g. washer fluid pump, regular horns, etc.). I thought I'd do some testing on the alarm system and try to get it functional, but now it seems like that could be a lot of time and effort. That little anti-tamper switch is broken - not enough threads to secure it. I tested it and it looks like with the button pressed the switch is open which tells me that leaving it out and disconnected should be OK. But even if I do that, there are a lot of other problematic parts like door and hood switches. Probably why the previous owner just told me not to use it because it drains the battery..... Might save this project for another day....
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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.