do you still have the bed??? my toy is an '88, and i moved the battery to the bed. i used either 2 or 4 guage, bought from a local electronics store. i think it's the type that the loud stereo people use. i stripped the end of it, and then covered it in solder, so it looked like it was dipped. went to kragen's battery section, bought a do it yourself battery wire clampy thing, which features two bolts that tighten down a bar over the end of the wire, then to the battery. the ground is straight from the shelves of kragen, a cute little 3 foot piece, bolted to a stock bolt location on the frame. also got a plastic battery box and a metal battery tray, combined the two so it wouldn't budge.
i was told that this little setup wouldn't work, that there'd be too much voltage drop in wire that long, and that the truck wouldn't even turn over. so far, i haven't had a single starting issue-both battery and starter are 3-4 years old. it's not the most high tech, but for a total cost of under $50, my battery is in my bed, out of the way so my front shock cage fits.
this could be put under the disco-tech section, i'm sure. how about POORFAB UNLIMITED???
hope this helps...