Before you buy any adapter, find out what size prongs the 2 pt implements have. I'm pretty sure your 3 bottom plow will have the large points (3 inches from top to bottom at the prong), but the 5 ft blade may be a small prong (2 1/2 inches at the prong). The small pronged implements were used on the Super C, 200, 230 and possibly the 240. The large prongs were used on the 300, 350, 400, etc. What IH tractors did your family have? Once you determine the implement usage you can look for the adapter. NOTE: You can weld a 1/2 inch piece of steel plate to the bottom of the small prongs to make them fit the larger 2pt system, but you can't do the reverse..) BobG in VA