95 roadmaster great car- 56k- too low

Heavy Duty Springs and an optional compliment to those springs either additional Helper Springs or Air Springs and an add on option to air spring would automatically adjust the pressure as load is being placed on the rear axle. All depending on your budget high performance front rotors and pads rear disc conversion for better stop and heat dissipation, could be very costly In power, I assume you want the car to accelerate quickly from stop or to be able to pass someone at crusing speed: For engine, assuming it has an LT1 engine, there are many upgrades you can do For those, possibly a torque converter upgrade, I am not sure what stall speed would be appropriate for that application. A rear axle ratio say 3.73 would give quicker acceleration and handle more load compare to 3.42 ratio, but would lose fuel economy because for the same given distance 3.73 rotates more than 3.42 ratio. I reccomend synthetic oil in engine and transmission and rear axle for less friction on components and withstand higher temperatures. Synthetic brake fluid is another suggestion to increase boiling point for better braking. Places to find these item, there are just to get started www.jegs.com www.summitracing.com http://www.gmperformanceparts.com/ Try local speed shops 1991-1996 Chevrolet Caprice/1994-1996 Chevrolet Impala(RWD) website fanbase, since I believe shares the same platform. Hopefully this gives you a good starting point