Just to muddy the waters - do you really want a VINTAGE unit?
A vintage (pre 73) unit would be free RFtax, but you still need an mot if carrying a load. A modern truck would require private HGV RFtax but it's only in region of £165.
As Glen said, a 4x2 would do fine. As allowable gross weights have increased then large fleets of 4x2s have been disposed of as operators go to 6x2s to carry the extra weight without RFtax penalty. This has resulted in lack of a market for these 4x2s and it has been possible in the recent past to pick up some cracking well-maintained 4x2 tractor units at really silly bargain prices (so cheap folk were buying them and having the chassis extended - not a cheap job - to turn them into beaver tail plant trucks).
And looking at Ray's superb Red Ball tribute on the 'Cab Art' thread, well you don't even notice that it is a modern truck!
Vintage trucks come at a price, and getting brakes through MOTs and sourcing parts is not always that easy - yes most parts are available but not immediately. If you need reliable (i.e. easily fixable at the roadside) daily / weekly / monthly transport for a vintage MV outfit it might pay to consider a modernish unit along the lines above?
It's just a thought :cheesy:
p.s. Did anyone buy one of those brand new Scammell Michellotti cabs being sold off at garden shed prices for allotment sheds or wendy houses a few years back? What a waste :-D