The UE diffs are just regular Hyper 7/8/8.5 with UE's diff output shafts while the Hot Bodies are hardened diffs. I don't have any experience with FLM's hybrid bulks but I do have UE's VBS bulks GA bulks with UE's 8 and 6 spyder gears respectively. Setup is easier on the VBS compared to the GA bulks.
If I were you, I'd buy the UE diff outputs from UE and the Ofna or Hot bodies diff from ebay and the GA or FLM bulks. This will cost you less than $200.
UE's VBS:
GA bulks with captured hinge pins:
Ofna/UE 8 spyder diff:
