Since you don't know what your cam lift is you are going to verify that your spring you plan on installing are suited for your cam. If your lucky you might find the manufacture and grind # on the end of the cam. If this info is there it will be a simple manner of contacting the cam manfacture for the correct springs. You will still have to insure that they are intalled at the correct installed height and that you have no coil bind. The retainer to guide clearence should have been checked by the person that built the engine but since you're having problems I'd double check everything.
If you can't verify your cam you'll need a dial indictor and check your lobe lift and mutiplt this figure by the rocker arm ratio to get your vavle lift. By know this and the type of lifters you have ( hyd., flat, solid roller, hyd roller) then you can go shopping for springs.