Just spent the last 10 days acid washing etc my old tank and guess what? http://www.coolairvw.co.uk/Item/New_Products~New_Parts_for_Buses/SK30688/T2_73-79_Fuel_Tank.html
Remember doing mine in POR 15 or something like that....put a new sender, breather hoses and filler neck in at the same time...great job to do if you're pulling your motor...can also do a bit of sound deadening while your at it
How much? Rust free imported tanks go for about £100 and are just as good and possibly better. Are they getting hard to find? I remember when JK started making a tall rear corner repair panel - they cost more than a whole genuine corner did. Doh!