Ok, so I ordered 2 new fuel tanks for my 1987 V10 long bed with dual tanks. I ordered 2 of the 16gal ones. So then my lmc catalog comes while I'm waiting, I'm flipping through it, come to fuel tanks, and it says that long bed trucks come with 20gal tanks! Sonofabitch. So I'm checking forums (mostly this one) and can't really get a total consensus except that about 95% of people agree with LMC. A couple people said '"I've seen 16s on a long bed like once". One guy said "nope, 1986 they switched to 16s". One guy says "my 86 long bed came with a 20gal" etc etc. I get home from work today and measure, and it definitely looks like a 16gal. Then one of my tanks came in, and its confirmed. I have dual 16 gal tanks stock. (thank god). But what the hell is the answer here? You guys are the experts, so I figured I'd ask.