Gearbox specs and dimensions

[LAV-25a]

Hello all, this is my first visit to this site, I hope this is the right place to post this question. I'm working up ideas for a 6x6, and I'd like to make it 3 speed capable, got a couple questions that I hope someone can answer:

First, is there any difference between the Tamiya 3 speed semi gearbox and the Hi-Lift gearbox other than the fact that the Hi-lift has two outputs? I've seen an ad on eBay that says that the gear ratios are the same, but I just wanted to double check that they were otherwise identical (durability, size, etc). I plan to use a transfer case, so if the single output gearboxes are pretty much the same as the ones on the 4wd, I can save a couple bucks.

Second, could someone be so kind as to give me the rough outer dimensions of the 3 speed gearbox. Even a couple of pictures next to a ruler would be a great help. I like to model things out before I shell out cash to see if they should work out (not that they always do, but...), and I know that the 3 speed gearbox is a pretty hefty chunk of machinery.

Thanks in advance

-val

[McFig]

Hi-Lift Gear Ratios
Low gear > 2nd gear > Top gear
1:64.39 > 1:35.20 > 1:21.14

Semi Gear Ratios
Low gear > 2nd gear > Top gear
1:32.49 > 1:17.76 > 1:10.66

Yes, the Hi-lift has two outputs and the semi has only one. Also, the Hi-lift motor sits on top of the gear box and the semi's motor sticks out the front.

Here is the Hi-lift tranny:
http://thescalerstore.altervista.org/catalog/images/hilift_gearbox.jpg

Here is the Semi tranny:
http://thescalerstore.altervista.org/catalog/images/hauler_gearbox.jpg