The problem with the OriginalSEX is that it's so old, there are too many mods that have been done in the past!
There was a parafeed version for a while, called ParaSEX. It used the original output transformer as plate choke, with the speaker winding as cathode feedback for the paralleled power sections, and a 4K line output (similar to the Speco we later switched to). There was a conversion manual as well.
The other problem is that there were three different power transformers, and they created different voltages. Add in that we revised the currents a bit at some point, and it gets confusing!