I am a recent subscriber to Gremlintime. While I can't say for sure that the pieces you have already aquired from a spirit will work on your Gremlin common sense says probably. I do however have quite a bit of experience with Hydraulics and disc brake conversions in general. You would be best off with the powerbrake booster/master cylinder assembly in total from the Spirit as well as the parts you already have. Also check the diameter of the Spirit rear wheel cylinders vs the Gremlin ones. While you are at the conversion consider replacing the brake hose at the rear differential if it has not already been done. Remember that cleanliness is absolutely essential with the hydraulic system. De-natured alcohol is the best substance I've found as it leaves no residue. It can degrade rubber components however so consider rebuilding any components that require more than just an external wash. Crocus Cloth should be used instead of Emery Cloth or Sandpaper. Any component that requires rebuilding should have its piston to bore clearance checked. A small piece of brass shim stock .005" thick should not fit between the bore of the device and its piston. Hope this is of some help.