I have a TD15 150 series gas start 554 engine w/straight dozer blade. Seal blown in 1 blade cylinder. Runs but lots of blowby, runs OK with a miss now and then on gas, dead miss on diesel, I'm guessing starting valve or injector problems. Don't suspect any cracked heads as no pressure builds in coolant tank. Rebuilt carb, new plugs, wires, cap, points, etc. Pads, sprockets 90% or better chain 0% stetched out, rollers appear OK but don't have the  specs so don't know. Tractor appears good, believe original paint, not beat up, welded up, etc.. No slop in levers, shifters, etc.. It has a homemade ROPS and limb risers I want to keep for another tractor. First $4000 owns it, lowballers it will scrap for around $3500 and and sell a few parts easy to get $4K so don't waste my time if you can't afford it. Hate to scrap it but don't have time this year run down hard to find parts and fix it. Have several service/owners/engine manuals too. Call or text 618-292-9274, calls usually go to voice mail but I'll call back.