1. Yes. Unless you want to drill the plastic yoke holes to 8mm. I had done it before and it works.
2. If I were you,I'd buy the Ofna Hyper 7/8/8.5 diffs. They're the same as the HB diffs but cheaper. I used those on my trucks. You can get them from ebay for $30 shipped each.
Are you going to use the stock plastic axles? If so, you also need the modified diff outputs. You can also make those buy buying revo stub axles and cutting off the threaded portion. I did that before too.
Here are some pics:
Plastic yoke drilled to 8mm:
With 6 spyder pinion:
Ofna hyper diff:
Modified diff outputs on the foreground (4 of them):
Here's a link to the revo stub axles you need in order to make the diff outputs to allow use of the plastic driveshafts with a buggy/truggy diff.
http://www3.towerhobbies.com/cgi-bin...?&I=LXHFY7&P=7