I have an older Grasshopper 720K with a 61" deck. I bought it with a broken rod in the Kohler CH20 engine. I only paid $500 for it. I always have to figure out why things died as I work on them. This engine was fully covered with grass and dirt, a good inch in most places. So, there was part of the story. But it was the $7 crankcase hose that was hard and cracked, which kept leaking small amounts of oil that fed the grass and dirt build-up. That reminded me of the $5 oil filter seal on Onan engines and how many rods have broken due to the lack of cooling on the filter side of the engine.
I was able to save the engine. I was lucky on that one. I do not know what the cylinder is made of, but it was amazingly hard and even slippery. The engine did have issues that made me give up on it. Someone else had taken it apart and had torqued the majority of the bolts to just below the point of pulling the thread, and a few were pulled already. I used the proper torque guidelines, but the bolts kept pulling the threads later. I eventually got tired of doing the thread repairs. It kept leaking oil when the bolts were loose.
I ended up buying a Kawasaki 25hp repower. That engine is pure silk and fires like it knew what I was going to do when I sat in the seat. The rest of the mower is so much like Ingersoll. Everything is designed to be like building your own mower, aiming for an easy and durable result. The only weak part is the factory when they are brand new, by what I see on the Gassopper groups. But most of those guys wouldn't know how to use a screwdriver with interchangeable bits.
That is a front mount, and it will only be used for mowing if I have a big yard. The only thing I miss is how long I get to listen to music, which is so much shorter.
The best front mount, in my opinion, is the 725D with the 61" deck. There has never been any dispute to this on the Grasshopper sites or dealers. They sell so many of them that the factory cannot keep up with the demand. They track dealer inventory, and during the mowing season, you are not allowed to have more than one 725D in stock.
The only issue with buying them is that the radiators are tough to keep clear. The temp gauge indicates they are running hot, causing the tractor to shut off the PTO power. That allows you to keep driving. Then you get the guys who swear the radiator is clear, and it is still running hot. Radiators do not lie, just like carbs do not lie. If everything is clean, it will run perfectly. Grasshopper has a cleaning wand that guys say works very well. You also have guys saying that they were wrong once they removed the radiator, too.
Do not let anyone convince you it is a Gasshopper problem.
My 720K has a standard seat that has a wood base seat and a stapled-on cover. I just bought high-density foam and new black vinyl. Then I run the tires at 6 psi like the manual says to run. I use a tire gauge that is for low-pressure tires, which is a 0-20 psi range. The ride does not bother me at all. Plus, that gives you the best traction as well. I haven't slipped out of the seat yet.
Harry