I've been running an early 80s 5050 now for 2 years as my mowing and small farm job tractor. Got it for $3k and havent put anything into it. It turns out mine is actually an orchard model - final drives rotated, exhaust exits down and rear and the fenders are round. Supposed to be lower for clearance under trees. I have hills on my property and the lower stance really makes for confident mowing across slopes. Never seen another one so they might be kinda rare.
The steering is very light and the hydraulics are strong which is impressive to me for a 35 year old tractor. The tractor is very fuel efficient.
Mine has been blowing white smoke and pushing oil out the breather and has gotten to the point where i had to pull the injectors and do some diagnostics. Pressures were 230-50-230 psi. Manual says spec is 370 rebuild under 320 psi, so the head is coming off and new sleeves and rings are going in next month. The CAV injection pump is leaking like a sieve as well, so thats getting a rebuild. All told I should have a tractor good for another 40 years for $500 and a few hours of my time. It ran like a beast with only some power coming from 2 cylinders - it will be awesome with all 3 working. Just finished cleaning and calibrating the injectors - that was another job that couldn't have been easier.
Some have said that bleeding the fuel system was hard. I disagree as long as you follow the procedure in the manual. There are about 7 points where you need to bleed in order so that you logically remove the air from the fuel system. Tractor will start right up - skip a step and not so much. Procedure works every time. Winter starts are easy with the preheat.
This machine has hooked me on the AC equipment and I will probably be looking for something in a 70-100 horse model next. Good luck, PSUAJ