tanks, tyres and general transalp confusion

[scdan3]

I was told (by a bloke in a pub...) that africa twin tanks fitted transalps. so when an africa twin tank turns up cheap locally i buy it and (brace yourself...) it doesn't fit. (the fitting cups are too far apart to grasp the frame, and is just the wrong size and shape).

I am thinking there is more than one type of africa twin tank? my translap is a n reg import, single front rotor, (so i assume a pd06). god only knows what AT the tank came from, it is white blue red with "adventure sports" graffic, with a single fuel tap at the rear, in the middle, underneath (if you follow...)

am off around the americas (top to bottom), so do really want a 250+ mile tank range... what model tank do i need? does anything else (cheap) fit?
(oh, and anyone want to buy a good condition AT tank? )

On an entirely unrelated subject, what are rimlocks and will i need them? there is a lot of talk about them, but, to be honest i just haven't got a clue.... (will be one up with ally luggage (thanks caveman). am not going out there to ride dirt trails for fun, but not scared of them either. (and have no idea what to do with tyre pressures. will work on a "suck it and see" basis for that one i think)

thanks in advance for all advice

dan