Haha way ahead of you there, I picked up the Snagga box for some more Savage Orruk Brutes, here's the first 3 before I based them. Their arms scale perfectly with Savage Orruk ones, so source those for converting.
Edit: before I sold the Squig riders, I noted they're small compared to Gotegruntas. The Nob on Squig is about the same size and bulk of a Goregrunta though, considering you get 1 per box you could easily source a load for a whole unit of Squig riding goregruntas.