Ok, so a few people asked me to look into this. A very nice man (JThiessen) sent me a piar of revo bulkheads to experiment on. Here is the result:
Needs a slight amount more work to get the bulks to touch without a little bit of flexxing. This is definately the cheapest way to get good diffs in a revo. Expect my 1521 powered revo to have lst diffs...
For anyone who is not familiar with lst diffs, they are 1/8 scale 6 spider design diffs. You can get a variety of different ratios for the ring and pinion, and a variety of different materials for those gears. Losi make a nice heavy duty plastic cup with steel inserts for the cross shafts. That cup is lighter than an all al cup and has plenty of strength. The also have tin coated ring and pinion gears in 13/43 ratio (stock lst ratio). 8b and 8t gear sets will fit the cups too. Big bearings for the pinion, which has an 8mm shaft. I may detail the varieties of lst diffs in another thread, for those interested. These are stout diffs, and cheap on ebay, usually 20 bucks for the diff in the case. There are a few different trucks that use these so parts are easy to find.