what is the widest rim that fits a 1960 kg ?

48 off set on what width wheel??

Do you know what is on there??

If you can do some measuring of an existing and then have a play here...

http://www.1010tires.com/WheelOffsetCalculator.asp 

you should be able to work out what you can get on there

I've got 5" radars with an offset of +20 , they fit with no problem. much further outwards and you will hit the guard on full lock over a bump ie: car park humps.Thats what happened with the stock 4" wheels that had been spaced out by 12mm. (disc brake)