If you have your old shield and gasket out, does the new one fit OK without the shield? Is it too long to fit in? I am not sure why one would need to cut a gasket. There is a trick of using a piece of heavy string to pull the gasket in place. There is alos a tool for this but I used string. You need to lubricate the gasket and metal (car) with perhaps spray silicone or liquid dish soap works.
Not sure of the configuration of the XK 120 but normally the gasket is placed around the windshield. Place one side in and the have someone press against the windshield and pull the string inwards. If all works well the gasket simply goes in place.
It is a bit more than I have explained but I think you can find something on the internet with better instructions.
Again I would see if the new gasket by itslef seems to fit well.
Does the new gasket look exactly like the old?
[ 04-09-2004: Message edited by: Bruce Bowker ]</p>