I bought kind of an interesting little U puller today. Its not a red nose tractor but it does have a single block. It has an LE401 crankshaft that looks to have been turned down to fit the stock U rods,I dont think its offset ground. It has 4 3/8 M&W pistons in it with a 1/2 inch spacer between the block and the crankcase. When I took the plugs out I discovered I needed a 13/16 socket not a 7/8, It has small plugs Like a chevrolet, I beleve they are AC 45 and there are no adapters. Whats the deal with the small plugs? Late replacement? LP? I have never seen an HC single head with small plugs myself. Anyone played around with a single block puller? How many ponys is it good for??? 75??