This weekend at AutoX one of my competitors noticed that I had liquid dripping out of the front of my car. On examination, it turned out to be Gasoline

. When I inspected, it was coming from the plastic tank in the fender well which has becomce very brittle and chunks have fallen off. Combine that with a full fuel tank (ooops, I know it is not the best for AutoX) and fast turns at AutoX, I managed to get some fuel sloshed into the tank.
I got a replacment tank from a local used parts place but it is for a later model and, naturally, it does not exactly fit where the original goes.

I have a 1973.5 911T and the tank is from a 1988 911.
Any help/suggestions as to how to mount would be appreciated.
TIA
Harry