Max tyre size different on ss springs?

I run that size Nitto Drag Radial on my '68 Barracuda convertible on an 8 inch rim. I forget the back spacing. The tires don't rub anywhere, are rated to 186mph and hook up very well on the street. They don't hook as well as a dedicated slick on a prepared track though.

I do have 3200lbs SS springs, but they fit the same as a stock spring as far as spring size etc. The car weighs 3700lbs without me in it, so it doesn't sit to high in the back.

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Still not a Dart...