Hi, I looked at the iroll site. They have the Panasport wheel in 2 offsets, 12 and 20.Somewhere on the wheel you should see either ET20 or ET12. I don't know what the ET part means.

All 240's I know back to 1980 use a 20 mm offset on the stock 5.5 inch wheels. I think the 15"x6" Volvo alloys have a 25mm ofset, so If you have the 12mm offset wheels they will need spacers to move the wheel out 12 or 13mm.(1/2 inch).

That's my best guess but don't buy anything without getting a second opinion. I think Iroll could help you out. Something else you could do is put a 1/2" worth of washers on 3 of your wheel studs and see what the clearance looks like with the wheel on.