Didn't have much time to mess with the truck until this evening and when I did I decided to focus on my gear reduction and transfer case solution. First things first I looked into how the tranny is going to interfere with a front driveshaft. Obviously, that's definitely got to be addressed!
I think I've narrowed down my drivetrain choices to these:
1. Use an Axial 2.6:1 trans as a transfer case and possibly a 2:1 planetary gear reduction in front of the Tamiya transmission.
2. Use a planetary gear reduction (probably 2:1) and add a t-case like the 2.18:1 RC4WD Disruptor or the 2:1 t-case from wtbcar.com:
In either of these solutions, the stock Tamiya tranny needs to be raised up fairly substantially....for two reasons. As mentioned, the tranny will prevent a driveshaft from reaching the front axle, but the 2:1 planetary will hit the steering/shifting servos because it'll push the motor forward. My best guess shows a height of 15-20mm is needed. Here's a rough approximation of the height required:
The floor will need to be trimmed, but I'm okay with that. I can always just build a simple cover for it so the trans is hidden from sight. My first estimation of where it'll need to be cut (everything within the white markings).
So before I order some standoffs I made some temporary 15mm spacers to see how that would work.
Driveshaft clearance should be okay with the trans raised 15mm, especially since the trans output will be fairly low.
Front view showing the height of the motor compared to the servo. It'll be reeeeally tight, but I can easily add a few more millimeters of spacers if need be.
Thinking this is what I'll need to cut away to accommodate the new trans height.
So now I need to decide what to do about the transfer case. I have an Axial trans so that's the cheapest solution. I'll just have to fab up a bracket for it. And it'll definitely get the outputs low enough to clear the stock trans. The wtbcar.com t-case looks like it would bolt in after drilling a couple holes so that'd be super easy, but it would cost me ~$50 and time to wait for shipping from (presumably) China. Not sure I'm patient enough to do that. Ha!