You got an awsome deal. The vast majority of the mowers out there are all the same. If it's a Sears, Murray, Bolens it was made by AYP. Go for the pressurized oil system w/ filter. If all you want to do is cut the grass, it doesn't really matter what type you get. If your yard is hilly or has obstacles you have to cut around, go for the hyrostatic drive. If it doesn't, save the couple hundred and get manual transmission. I have the 17hp, 42" cut Sears w/ hydro. Mine doesn't have the oil filter. Should have spent the extra money for the larger motor with the filter. I cut 3/4 acre and use the dump trailer to move logs, dirt, mulch, shrubs, trees, construction materials, etc. It does everything I need it to do. I bought a 1968 Sears Garden Tractor w/ plow blade in the spring to use to plow the driveway this winter. I use it to pull my boat (19' bowrider) around the driveway and get my utility trailer from the back of the lot (where I can't get the van). Now I just need to figure out how the wires go on the '68 and finish rewiring it so I can have it running again by winter.