Ok, Here is the way I would go about it since you want the pinion centered...Get the housing you want to use, either buy a pinion centering gauge, make one or my preferred method for centered pinions...Get a Third member that has at least pinion & yoke in it, put it in housing. With some scraps you can make a pointer set-up that rotates on the pinion bearings for accurate measuring that can be made in an hour that will be well worth it, I can explain it in more detail if you would like .
Total from wheel flange to wheel flange is what measurement we are interested in. Forget about the measurement from housing end to housing end at this point. What is important is axle flange to axle flange (total between your wheels) & then subtract from there. There are different thickness housing ends & axle set-out (distance from backing plate to axle flange) to add to the mix of things to foul you up.
Give that measurement & we will continue from there, no rushing here, we don't want to end up with a too short of axle or Two. By the way... No your axle lengths are not correct.