OK, I sent them the specs of RallyBob's Springs..showing stock is 150lbs. They came back in said, there records show stock as being 140lbs, but they could make either. I read a few posts that say the GT rides/handles better with SOFTER rear springs, due to the geometry of the rear suspension...so should I go with the 140s?? I will be installing Koni's at a later date, so whatever works better with them.
150 lbs is what they told me about 10 years ago, with the OEM Opel 'reinforced' rear spring set being 160 lbs. This was a factory option for an upgraded suspension package, which was never offered here in the US, but in the mid-'90's I got a few NOS sets of them from Germany.