Digga Stompas were made by Epicast and matched the size of the original Epic stompas. Current WH 40K stompas are larger that the Epicast ones. I have a few of the Epicast ones, in both versions. Below is some information I found for using them in WH40K (Apoc) games.
- Da Art of Waaagh! datasheet and formation, 300 points, link