The 8 spiders for the hyper 8 buggies will work too.
In fact, the diffs from hyper 7/8/8.5 are almost identical. I said almost because the only difference I saw is the following:
1. Hyper 7 diffs use an o-ring as seal between the ring gear and cup
2. Hyper 8/8.5 diffs use a paper gasket as seal between the ring gear and cup
Other than that, everything is the same. I have the 6 spider version of each of these.
You can also use the diff from a Kyosho ST-RR truggy.
Here are some pictures of the Hyper 7 and Kyosho diffs:
Kyosho diff:
Side by side with the hyper 7 cup:
Various diffs; Hyper 7/8/8.5, mutilator, savage I tried during my experimentations last year.
These pictures were taken for somebody in the UE forum asking if the Kyosho ST-RR diff will fit into the UE Ultralite cases. They will. I took measurements using my digital caliper. Anyone who wants these measurements can pm me their emaill address so I can send you the info as an attachment
.