dicast cars suspention.

FocusOne is right, all diecast cars are made differently. In basic terms, you'll probably have to either raise the wheel or lower the body. usually the best bet is to glue in plastic blocks or rod to offset vertically the suspension, body or wheel. The last one i did, i literally cut off the axle boss and glued it back on at the right height to lower the car, then put the wheel back on.

that really depends on how the suspension was manufactured (on the model, of course).  For starters, what's the brand of the diecast car?  can it be taken apart or is it rivetted together?  Any pictures?