Wheel diameter

[Austin in the Shed]

Charles, that certainly helps. My 17 inch wheels have 3.50s X 17s at the rear and 3.25 X 17s at the front. I had thought that changing the FDR this way not only changes the FDR but also lowers the CG. Am I missing something regarding this hill climb and the optimum FDR?

I think Charles is limited on wheel dia by the VSCC regs.If I were you and was only going to use the car for 1 hill climb event and for road use out there I would leave the 4.9 axle in and just swap the wheels,and it does lower the c of g a bit.
I feel the 4.9 ratio is good if you don't have too many steep hills to climb and doesn't feel under geared on the flat especially if you have a reasonably powerful engine.
If 3 speed box yes C/Ratio