I'm not sure if that is a serious question (putting a '68 tank
in a split window) but if it is, I did it.  It is a close fit
and you have to make longer straps to hold it in, but it does fit.
I made the mistake of keeping my '67 gas sender, so the guage read
though the tank ran out at about ~ 12.5 gallons.  If I did it 
again, I would also install the '68 sender.
				Forrest Minor