Before you throw out the "A" word, on which brand to choose, since we've already convinced him not to choose chemtex...consider this, the owner of amtex used to be partners with chemtex, they have a very similar heat exchanger design, they both DO NOT use water boxes (which causes overheating), they both use rubber hoses with galvanized metal (which causes rust throughout the entire system), they both use the same temperature gauge (which cannot hold up to the heat, and WILL fail) etc. etc.
My opinion, the amtex is a dressed up chemtex with a few minor modifications.
Do your research before you make a big purchase. What do I mean by research... Find out who has these truck mounts, and CALL THEM. They won't type the truth. They're too scared the manufacturer will read their feedback. Believe me, it's true.