Beautiful car, congrats on the buy. Personally, I love the way those AR61 rims look on a Monte, but I understand wanting to go back to stock as well.
I just picked up my own weekend cruising/occasional commute 88 SS. It's nowhere near as nice as yours, so not as much a target for theft, but I still bought full insurance coverage ASAP. I went through my regular insurance agent - they got me $0 deductible classic coverage, $5000 guaranteed valuation on the car (I'll raise the amount when I get it fixed up the way I want it), full fire/theft/vandalism/collision, 250/500 liability, total premium of $235 a year.
I know you're taking anti-theft measures, and so will I, but if a thief wants your car bad enough, they're gonna get it. Next best thing to having your dream car? Having the money to buy another one if the worst happens. $20/month (probably a bit more, since you'll probably need coverage for a valuation more in the $20k range for a car that nice) is not much to pay for that kind of piece of mind.
Yep I prolly sound like an insurance salesman, but I ain't - I just can't stress enough the importance of good coverage, with how rare and desirable 4th gens are getting.