I think I may have the lower that you are looking for. I have a Original Preban Colt
SP1 Lower .223/5.56, Large Hole. I have installed a Rock River 2 stage trigger in it of which my gunsmith converted to a very light trigger pull. I have the original trigger that I can reinstall. I also have the orginal grip, or you can have an ergo grip (black) to go with it. I want to keep the stock, but I will sell it with the actual buffer tube and spring assembly. This is a very good lower, in very good condition. SLAB SIDE. I live in KY, get back to me @ email@example.com with an offer or questions if you are interested.