Looking at the power graph, the power drops off above about 7200, if this is accurate (is it?) the shift point should be set (on the gear chart and in "real life" at 7200rpm), this will change the top speed to about 150mph in 5th, the close ratio 'box looks good, with nicely spaced ratios,(apart from 2nd being a bit high), so if i were you i would opt for the close ratio 'box, the power band on your engine is much narrower than i expected, it has a lot of power and torque over a relatively narrow band, even with the close ratio box, i recon it could drop out of the power changing from 1st to 2nd, a more progressive power curve with the power coming in below 5,800 might make it more drivable and potentially quicker on the track, especially in the wet
if the change points, are changed from 7600rpm to 7200, then, 50 will be in 1st, 80 in 2nd,100 in 3rd,130 in 4th ,150 in 5th, if 2nd was lowered untill it did about 75 at 7200rpm, it would be less liable to drop out of the power from 1st to 2nd, and will not drop out of the power 2nd to 3rd, in fact right at about the peak torque (so overall the car will accelerate quicker)
the final drive would be set much lower to get a really quick time, you could set it to be redlined ("redline" = 7200) in top (or 4th, and only use 5th for the road) (with a couple of hundred rpm to spare) on the longest straight of the fastest track you are liable to be competing on, (i recon this would be a good overall compromise) this would make the gearing much lower, and the ratios closer the tractive effort would be further increased, and the acceleraion, but also the torque from the torque multiplier would also be increased, i mean gearbox
you can use a video camera with a view of all the gauges as a basic "data logger"
ive never been involved with hillclimbs but i would imagine roadholding/ handling (and traction) plays a big part - have you done your corner weights?
i remember seeing a video of a kart on a "demonstration run" (not officialy in any class ) - its time would have beaten every car apart from the winning 1000+Hp 600kgs modified old F1 car in an open class, the kart had less than 80Hp!
What a beast of a machine - DR jeckle below 4.8k and Mr Hyde above!