http://www.ytmag.com/ttalk/messages/6206.html (1920's and 1930's saw a
host of homebuilt farm tractors, a lot of them better than commercial
ones. Model A engines and transmissions were favored because they were
lead pipe simple and hulletproof. The now more numerous VW Bugs would
work as well, as would practically any junked vehicle with a good engine
and transmission---you will need a truck rear end though, and its a good
idea to keep the front part of the passenger compartment (and install a
rollover bar inside)..
Any homebuilt needs an auxiliary transmission to increase engine torque
to rear wheels, or a two-speed truck axle should suffice. There are
commercially available hydraulic pumps and three-point lifts which you
would want to install on a homebuilt to make it useful. Also to get
sufficient traction you would want large diameter, heavily cleated truck
tires and wheels to match, plus wheel weights, or weights over the axle)
http://www.cadplans.com/ (every farm tractor, commercial or homebuilt
needs a front end loader, and a backhoe is almost equally useful. I
know the guy at Daleville and the quality of his kits or assembled
equipment from licensees is excellent)