I am restoring a GMC stepside 1978 in Ireland, and have currently replaced all wings and doors and recently purchased new engine.  I am not happy with the height of truck and currently running 15 x 8 rims on a 33 x 12.50 tyre and was wondering how low would you recommend lowering suspension and would 2.5" drop spindles and spring shackles and hangers bring me down enough that tyres would reach top of arch. Or would I need drop spindles and springs in the front and axle flip kit and C-notch in the rear.  Any advice would be greatly appreciated.  

if you want the top of the tires to be even with the wheel opening in the fenders just measure the gap and drop it however much the gap is