I have an AC model B210 that I purchased at a yard sale 5 years ago. $450.00. It ran and pulled fine. I rebuilt the transaxle (straight shift) the first winter. Very heavy automotive style gears. Total cost $200.00. Last year, I rebuilt the mower deck and converted from the older double V pully to the newer single V style for the mid PTO. Total Cost $150.00. This tractor originally carried a 10 hp briggs engine. The previous owner had worn that out, and installed a 16hp Tecumseh cast iron pump motor (electric start). Because it is a pump motor, it has been installed backwards, with the flywheel bolted directly to the shaft. (slight elding appears to have been required.) This 30 years old gadget still works great. Only 2 problems. First, the Tecumseh is a little heavy on the front end, which can make steering difficult. Second, if the deck clogs up you've got a smoked belt immediately. But, Little Allis will plow snow almost as high as any pickup, cuz I can climb right up the banks.
Simplicity is a solid brand, with parts available even for 30 year old equipment. (If a might expensive). Replacement parts seem well machined and fit snug to tight.
A history of the Chalmers L/G tractors is online at SimpleTractors. Am new to this, so I will try to find the link and post it later. There are a lot of pictures, including attachments for these old girls. (Trenchers, Post hole screws, etc.)