At times the position is marked on the frame with small punch marks. Pic below will give the approximate position. There is not much room between the rear engine mount and the brake rod anti-rattler mount. The spare wheel mount base pictured, has been removed from the frame (before I obtained the car) and should be securely riveted in place.
Let me know if you require some actual measurements to go by. The nose cone in the fender will have to be precisely cut in the right position also.