Perry,

If you had the CAD drawings and were willing to share, perhaps you could convert/scale them to size and release a PDF of the sideview of the two sides of each gearbox. Then people could print it out (and hopefully it will print out at the right scale being a PDF), tape them to a piece of sheet metal, and have a template for drilling, cutting and bending.
Might not fit every tank, but it would save some others having to experiment with dimensions themselves.

David