On my '65 and '66 both have tanks inside the cab and I don't have any problems.
On my '53 I moved the tank to between the frame in the rear just to get more space in the cab. It's a pain to fill because you have to be really carefull not to drip gas on the bed wood, but the added storage space makes up for it.
On the '59 the PO moved the tank to the rear and routed the filler tube to the left rear fender using a custom welded pipe. I'm keeping it this way for 2 reason, I like the added space and I don't want to weld up the hole in the fender (okay I'm a little lazy).
And on the '41 the jury's still out if it's getting moved or not.
