The tractor and loader both look to be in good condition, but they are not a great match. I'm not putting down the tractor or the loader, just noting things to be aware of.
Were those loader brackets originally intended to mount it on a bigger longer tractor, like a 706 or 856? The right hand bracket by the clutch is held on by one bolt and the left hand bracket has two bolts. It looks like a good heavy duty loader, but it is too far back on that 656. It will be very tough to get on and off the tractor. When you test drive it take the time to climbing on and off it at least 6 or 10 times or more and don't be shy about complaining about it if it bothers you. The seller is already very aware of it and knows that it hurts the selling price.
It looks like there is a HeatHouser/weather break mounting bracket on the tractor's cowl. One would be great for keeping warm while pushing snow, but with that loader you would almost have to leave the left hand door off to be able to get on and off the tractor. You will also have to leave the right hand window open to reach the loader joystick.
How wide is the loader bucket? Can you move the rear tires and fenders out further to get more room to get on and off the tractor? That would also increase the tractor's stability a little.
The tires are older and cracking, but are still usable with the chains. Check that the rear tire have fluid in them, you'll need it with that loader. Check the front pedestal over well. 7.50 wide front tires would be nicer with that heavy duty loader. A narrow front end is OK on a loader tractor, but it will reduce your trade-in value by $500 to $750 less than a WF. Is that the battery on the platform, that will get old very fast.
The loader is probably about about as old as the tractor, it's not a quick-tach loader, Westendorf had some great quick-tach loaders by 1970. With a quick-tach loader that would become a very handy tractor. I'd value the loader at its trade-in value (less than $500?) and negotiate as if you intend to replace the loader in the near future. After you climb on and off that unit for a few months you may want to do that anyway.
Can you get copy of a loader's manual or mounting instructions from Westendorf to see what the original mounting brackets for a 656 looked like? If that loader can be moved forward on the tractor by 6 to 18 inches it would be a much handier combination. You can put an extension on the joystick handle and extend the brakets going back to the rear axle. A welding shop might be able to move the loader for a few hundred dollars. Please confirm that before negotiating on the tractor.
Both the tractor and loader look to be in good condition, they just don't work well together. Good luck and don't pay too much for that combination as it is. What is the asking price?