Bottoming out and trying to fix this problem

Hey guys, I'm having a problem with bottoming out whenever I go over a harsh dip in the road. I think that its the plastic cover on the gas tank, not positive though, but it sounds like thats what it is.

Anyway, I figure it's either the straps that hold up the gas tank being broken or just sagging, or maybe the coil springs in the rear being cracked or worn out (since they are the originals).

So heres the question, I really dont want to replace the springs with lowered ones because I drive my car in the winter and I need the clearance. But I was looking at the local auto stores and they sell coil sets that are Variable rate. Are these the type of springs that come stock on our cars? If not, will it be alright if I get these as replacements?

I'm really getting sick of the sound, and I know its not the exhaust because thats the first thing I checked. Lemme know what you think

Thanks for the input. But I jacked it up today and took a really close look at everything on the underside of the car. I don't think there is bottoming out, at least not on the gas tank. I'm gonna put it on a lift in the next couple of days, maybe that might help.

WHen you say isolators, do you mean the things you put in between the coils to make the coils harsher/stiffer? Or do you mean the actually coil spring isolator, being the rubber or urathane parts that go inbetween the chassis and the spring?

yeah, I've used those before on my old 89. They work well. I supose it wouldnt hurt to try, at least as a troubleshooting measure. thx

k, I'll give that a try. I took a quick look last time I was under it and didn't see anything. Sounds like it could be that though. I'm also gonna put a little white out on different parts, go for a drive and make it make that sound then check it. Sounds dumb, but I figure I'll try. I'll let ya know how it goes, thanks