As I posted a while back in the rules section; overcoming the lack of Kustom Battlefortress rules in the FW Index looks easy enough:
Move, Strength, Toughness, Wounds and Save all as Banebleade Index Imperium 2 p30.
WS, BS, Ld as Kill Tanks from Forgeworld Index Xenos.
Points would be 300 + weapons and wargear based on IA 8 pts for Skullhamma and Custom Battlefortress less their standard weapons.
The simple way to add other weapons and wargear is to use IA8 points.
For weapons and wargear not in FW Index Xenos: Skulhamme Kannon in IA8 = Supa Kannon in 8th.
There's also no Grot Bombs but these have basically the same profile as a Leman Russ Battle Cannon in 7th so range 24-72" type heavy D6, S8, AP-2, D D3, BS 4+ twin linked and 20pts.
Of course FW may produce profiles before the weekend but if not here's a fix that seems fair.
Hope this helps.