Putting more HP in the car usually mean that you will have to do some changes in the back end or other things to the car. If you buy the car weigh it on all four corners. A friend that is real good with chassis stuff helped out with a twin turbo small block, small tire car back half car on a radial. It was making a 1.36 60 foot but being a twin turbo car the owner thought it was OK. My friend did not agree and finally after the season he talked the guy into putting the car on the scales because he thought it was to front heavy with the engine to far forward having not been set back from stock engine location, he was correct. He moved a lot of weigh to the rear location in the Car and put a little ballast in the back also and it went 1.19 60 FT. Took a complete season for the owner and others to listen to him and now they wish they had of in the spring not the fall. The Super Stock Springs might be to the end of their capabilities and you might look into Cals or something else for the future. A simple change to Cal and shocks might be you easiest next stop. Are you thinking of upping the HP even over 550 hp in the future or making this car a total drag car then maybe you can look at other choices.