Did you get any joy with this? I'm going through the same thing at the mo' having brought an old (1996) Bass 350 head back to Oz from the US. I expected to be able to get the schematic from SWR (Fender) as the info about it is still intheir FAQ section on the SWR website, but the support people at Fender are denying all knowledge. They've sent me a few post-1999 schematics, but nothing before that.
Anyone got the pre-1999 schematic?
"You can't talk about the drums without talking about the bass!"