8.5 or 10.5 in classic Ultima? Or too much???

[Boons]

Hi all,

I'm going to be running my Ultima with a shorty length ways inside the chassis with a modern brushless set up. As there is no slipper I'm concerned my motor choice will be too much for the light front end. I'm hoping the transmission holds out too! I seem to recall the ball diffs fitted to later Ultima's weren't very good? Could this 'act' as a slipper, or would that just wear the diff out?

Sorry for all the questions!

Cheers
Ryan