Since the Transit van was introduced in 1965 people have been customising them, alloy wheels has always been a popular option. Unfortunalty the transit has a PCD (thats pitch circle diameter) of 160mm x 5 shared only with the Tata. so alloy wheel choice has been very restrictive.
The most common way to fit alloys of a different PCD is to have adapters made (information on adapters can be found elsewhere on this site), an adapter is a block of metal that bolts to the Transit hubs and has studs which match the new wheel. There are a few problems with this,