CAB conversion

Hi everyone, am New to this place...

just got a 1963 88" diesel, galv chassis, 200dti, mostly series 3 body, would like to conversion it from van to a pick up with a cab can i just get a cab from Any series and it will fit??? Also want a canvas cover! how would this be waterproof between its self and the cab, sorry if these seem like stupid question but i am very New to landys
One last question, it would be great to keep up with traffic without screwing it to death, Any ideas about a different gearbox box with 5 longer range gears would be apprietiated...
Regards karl

Any series 2, 2a or 3 will fit but you'll also need a filler panel that fits between the tub and the cab. There should be a rain channel around the rear window which the canvas will go into to keep the rain out or at least most of it

Look at this on eBay http://www.ebay.co.uk/itm/401351702267

Also not sure about gearboxes but you can fit range rover diffs with a higher ratio to increase the speed

Thanks Marmaduke. I am guessing most LR bits are interchangeable...and I will look at the diff's but still think 5 gears would be a greater improvement..if anyone else can add further info I would be grateful.
Regards Karl