I searched all kinds of keywords and came up with nothing.
Anyone have an owners manual - or official figure - for what these Trucks will hold in Gallons ?
Or in Litres - i'll convert it.
Mine is an 81 if that matters.
Thank You
I think its 15 US gallons.
Thanks Spearco !
After i posted question - i sharpened up a little more and did a Yahoo search.
Came up with 60 liters - on hits from rockcrawler.com and vwcaddy.com
conversion = 15.85 US Gallons
I was expecting it to be about 12 gallon tank.
Was trying to decide if I should drop tank and adjust fuel level sender. Think i need to now for sure. Has about 4 maybe 5 gallons in it - reading half tank +.
Found another hit from rockcrawler that says 57 liters.
That would be 15.08 US gals.
I'm just gonna call the thang a 15 gal tank, like you said.
Mine had a 30 gal tank, and it barely fit.
Required suspension mods too
I think it's closer to 16 US gallons, from the amounts I have been able to squeeze into mine over the years while running on fumes...
I've got to drop my tank one of these days too, to fix the sender that works but must have become unfastened somehow, and the emergency brake cables and the rear brake hoses....not looking forward to it particularly as I had done it years ago....
Mine had a 30 gal tank, and it barely fit.
Required suspension mods too 
HOLY CRAP!

did that thing squat with a full tank?
with the bumpstops lowered 2" and the air shocks pumped up, not at all.