Mark... there are not really any options for a split dump for the R34's
I've looked into this quite a bit. HKS make some split dumps, but then you also have to buy the front pipe. Being HKS, you pay big money, and its just a damn pipe. I'm just going the bell mouth front dump. The gains to be had with a split dump over a bell mouth setup is not worth the many extra dollars imo. If just jap made a split dump, I would get it as they do a good price, but I spoke to them and they have no plans to make one for the R34
The just jap front dump is about $200 from memory, which is really good. I'm basically doing the same as you. 3" all the way. I've got a different muffler though. It arrived yesterday