Look here at this auction
http://cgi.ebay.com/Custom-GMC-Flat-Bed-Wrecker_W0QQitemZ220465829341QQcmdZViewItemQQptZSl ot_Cars?hash=item3354c995dd&_trksid=p3286.c0.m14

Do a search on Boley trucks. I think that is what they are.

You can get them here...
http://cgi.ebay.com/6-TOW-TRUCK-ROLL-BACK-WRECKER-HO-SCALE-1-87-GMC-BOLEY_W0QQitemZ390082490557QQcategoryZ223QQcmdZVie wItemQQ_trksidZp4340.m215QQ_trkparmsZalgo%3DSICDD% 26its%3DI%252BC%252BS%252BIA%26itu%3DUS-BWR%252BUCI%252BUCC%252BIT%252BUA%26otn%3D12%26ps% 3D33#ht_3764wt_1036

Yup Boley is the maker. CAUTION!!!!! Make sure you get the 1/87 scale!!! The 1/64 will be way too big for a conversion. For slot material, they do sell decent, but there are a few selling them now. I've found that they sit a little high with the factory wheels. They also aren't very good runners due to the set back pick up shoes. Keep these things in mind when ordering. It's very easy to start buying up trucks and racking up a big bill. The prices are decent, but you'll find the urge makes you want more!! :lol: