Hi Larry, Let me give you a more detailed description of what I did with the mast top fitting. The Dwyer fitting has much smaller sheaves than my old fitting had, so from my point of view, I wanted the larger sheaves, plus the ability of pulling the sheaves by removing a ring and pulling the clevis pin - goodness as far as I was concerned. When I took my original mast top fitting and tried it on the Dwyer mast, the geometry of the part fitting into the mast was wrong. So, cut off the top portion (with the sheaves) from the Dwyer fitting. This fitting had rivets instead of clevis pins, so that was no way of taking it apart. Cut off the part that fits into the mast from the original fitting. This give you the top portion with the sheaves. The Dwyer fitting was cut where the sheaves were, leaving you the lower part that fits into the Dwyer mast profile Place parts in vise and file until you generate flat surfaces so that the two parts can be fitted together. I then drilled and tapped two 1/4 - 20 holes and fastened the two pieces together. Then, I noticed that the original forward sheave was too far back and the halyard didn't lead fairly. It scraped at the edge of the fitting. Can't have that, so take it all apart again, and now drill a new clevis pin hole about 1X diameter further forward - I think I used as much space as I had available. Now the main halyard leaves the sheave on the forward side of the mast and doesn't rub on anything. Is this clear? If not yell! Connie