Who's still running w/ stock gas tank?

[70ChevyCST]

I'm at my wit's end with this gas smell in the cab. I thought I was on to something when I found that my 70 CST-10 (no vent in tank) did not have a vented cap on it. I bought a vented cap and the gas smell in the cab is still very bad. Every time I drive it (even with the windows wide open) I arrive at my destination reeking of gas fumes. I've sealed up the sending unit with a shallow metal peanut can and duct tape to "run a test" to see if that was leaking fumes....still stinks with the can in place....I've poked around underneath as best I can to see if there are any leaks....Obviously I can't see in back underneath completely without removing the whole tank...I'm just wondering if I need to remove it and locate the tank elsewhere....I hate to do it because I know it's going to be a big job. How many of you guys are still running around with the tank in the cab...in it's original location? Is it the nature of the beast? Does it have to be relocated to get rid of this gas stench or do I have a tiny leak somewhere where i can't see it?? There is absolutely no evidence of a leak anywhere, yet I have this nasty gas fume problem!! Please help with any advice whatsoever. I do not have a cardboard/carpet cover for the tank...Is that part of the problem?? Thanks, Bob