Even on the 1.0 gearbox I shimmed my rear diff. The only advantage to the 1.0 gearbox is that they were made out of slightly stiffer plastic compound which made them more rigid. The 2.0 design is much better. With the 1.0 gearbox the non-pinion side bearing insert could spin inside the gearbox = very bad.

As long as you replace the gearbox every now n' then, use aluminum inserts and shim the diff tight, the 2.0 gearboxes work just fine.