I have bought some heavy duty valve springs to run a high lift cam, but am wondering if I need stronger retainers or anything else to run the high lift cam? (wade 1521a)

I'd have no clue personally but have you asked any of the guys in the wade cam forum area for some tips?

when removing the collets make sure that they dont but tightly together over the valve stem, cause if they do and you refit them you run the risk of dropping a valve. There only needs to be a couple a thou in it but visually inspect each one before you pull the retainers off, then keep them separated and matched to each stem. Once you have got them off check to see if there is any polishing on the flat faces of the half moons and if there is then you will either need to get a new set of retainers or gently and mildy file a little of the faces of them. If you get new ones dont just assume that they will be perfect too, fit them and check them also. The retainers will be strong enough to handle the extra load