Hey Matt, Most of the conversion's that I have seen, are done with Bruder toys. Skidsteer loader's, wheeled and tracked, dozer's, excavator's and truck's.
http://www.rctruckandconstruction.co...ghlight=bruder
And they are on this site and the other site, that a few of us also belong to,
http://www.scale4x4rc.org/forums/showthread.php?t=44217 .
Search the forums for "Bruder conversion's'' and a lot of good info will show up. I don't know what scale you want to play with? Somebody has a video on youtube of a 1-50 O & K RH340, diacast model converted to RC,
http://www.youtube.com/watch?v=2Z8kX...e_gdata_player There are a few member's converting 1/16 Ertle farm toy's to RC also.
http://www.rctruckandconstruction.co...t=farm+tractor
Hope this help's!
Later, Neil#2 aka doodlebug