The standard steering wheel on a  Vokswagen transporter is 45cm with power steering/strong arms 40cm is OK, and still allows the reading of the speedo 36cm is too small to read the speedo, and to small to turn unless your name is Geoff Capes. There are several sellers on Ebay who will sell a "genuine VW steering wheel" that "fits" a T25 They may well be off a Golf or similar they often require some sort of adapter. On a standard van they you will find it difficult to steer with the reduced leverage of the smaller diameter. There are two main types of steering wheel made for the T25 one is the standard hard one that is usually on panels and campers, the softer feel ones were supplied with Caravelles and Carats and offer a nicer squidgy  feel. Find out more about the Volkswagen T3  type 2 transporter at www.club80-90.co.uk and also take a look at our wiki for more technical help http://wiki.80-90.co.uk/index.php/Main_Page