thedigler,

I can help with a few of your questions.

The spectrum receiver will work fine and I believe the speedo will as well (I've never owned one tho)

As far as angled or mounting the servo flat, this will start a debate. This is a good thing because I am thinking of mounting mine flat and would like some input. I do know they work well either way.

For hop ups I highly recomend getting the titanium front axels, new machined delrin A arms and the CRC front shims (anything but the washers that come standard).

The 16 ga wire is just lighter and a little more flexable so that it won't introduce a false tweek on the rear pod. Your only using 4 cells, so a heavier gauge is not needed, but what you have now is fine.

Lastly, you may want to get a bumper on the car till you get used to it to help keep the body from cutting the front tires as you bump into things.