Not sure about what the spring cap is, could it be the recoil spring plug that retains the front of the recoil spring? In any case, the standard weight 14# recoil is available from Wolff Gunsprings and likely others. My traditional Colt conversion kit, with "floating chamber", just used standard Government Model recoil recoil spring guide and recoil spring plug, available at Brownells, Midway, and others. Fortunately, the parts you mention are easily available, and relatively inexpensive. If you already have a Colt Government Model, you could just use the standard recoil spring guide and plug from your gun...