The diameter of the Borg Warner 35 convertor neck is around 3/16"ish bigger than the 904. Basic the company making the convertor machines up a stepped neck, the diameter that drives the pump is the standard size, the diamter that runs on the pump bush is the larger size. Most importantly, this adds thickness to the bottom of the drive slot where 904 necks are prone to cracking.
Basically every reputable convertor shop in Australia has this as an option (Big Neck). Autoflite Engineering (Dominator Convertors) were the first to do this many years ago. I have a pic somewhere, but I would have to dig it up.

AL....