I don't think it's the alarm draining your batt. unless it was wired in wrong. The alarm will only draw a few milliamps at most. It could be your battery going bad or a faulty alt.
If you want you could just unplug the brain box to test your theory.
Black,79 Mustang mostly carbon fiber/kevlar body, M-2300-k brake kit, full roll cage, maximum motorsport suspension, custom geared 6 speed, 2 inch rear fender flares, 1 inch front, motor being built (no eta). Looks like the Mad Max interseptor and weighs about 1800lbs w/o motor (450hp 351w installed to move the car around)
Black, 82 Capri RS 5.0L, B303, 1.7 rockers, World 180 heads, +150hp N.O.S, Turbo coupe rear end, T-56(tremec tko would be beter), 80 cobra nose