I have several different brands of walk-behind garden tractors and in my opinion the David Bradley's are the most "usable". Large tires so they put the power to the ground, good variety of tools that are easy to change, and enough of them around that parts are obtainable. Most that you see have a very basic drive system with a fixed speed with no reverse and ratchet clutches in the wheels. However, some later models had a neat variable speed sheave system, reverser, and a true locking differential. I have one of the former and one of the later which is the one I use the most. It will pull the plow about 4" deep in our clay soil and works very well with the cultivator and sickle mower.
M.E. Miller has tires to fit the different models (some had 16" while others were 15") but be prepared to spend $100+ each for new rubber. A pair of used 6.5x16 truck tires would also work, especially if they are traction tread. This isn't as "non original" as it sounds since you could buy new DB's without tires specifically to do this with.