Andrew,
I fully understand and feel for your situation. Unfortunately, it seems that anything can be considered a "modification" these days, but we have to find out which of these in particular will cause an insurance claim to become void.
If any modification will do, then your underdrive pulleys, stereo and even your Super Coupe wheels could be regarded as modifications, along with different size tires than "factory recommended". This is obviously a very grey area, so we need to get some facts out on the table.
Personally, I think you should keep your springs and shocks if you really like them. You can't let the police and insurance companies bully you out of your favourite hobby (besides the GF). I'm totally on your side, and I don't want to see you start to take everything off of your car because of these technicalities. It isn't fair for you or anyone else, so don't feel you have to lay down and die, along with all your aparent "mods".
Look at my car as an example. Why should I even pay insurance? If I crashed it tomorrow, they'd likely keep my money and tell me to drive it off a bridge, then refuse to pay for any damages, including liability. I know I have internal mods to the engine, which is quite different, but buying aftermarket suspension that sits 1.4" lower isn't that noticeable to the untrained eye, so I wouldn't worry TOO MUCH about it. I cop or insurance adjuster would have to know Thunderbirds to tell the difference.
I have the same urge to jump off the deep end, but I'm trying my best to resist in order to enjoy all that I've managed to build and achieve with this car (with the help of many others). I am still considering cancelling my policy until next year, hoping another year older, and some positive changes in the industry may help. I'm not trying to change your mind so much as I'm asking you to look at the big picture as far as modifications go. A modification should normally be considered something "performance enhancing", which usually pretains to power and the increased risk that goes along with it. In this case, lowering springs are in a grey area, in my opinion. Do they really increase the chance of being in an accident? Likely not. If anything, braking distance is reduced.
Call around to a few other companies, or ask a few brokers to seek their advice. You may find a company that is easier to deal with, and that doesn't carry such strict "rules".