Unfortunately, it sounds like you already have.
Stay away from the Nissan franchise dealers, unless you know them first hand or by recommendation that they know there way around 350/370/R35.
Best to try and save the studs that are part of the cats (front part of Y)
Yes, they can be cut off and replaced with bolts, however a bit of heat on the nuts should facilitate removal.
Thanks, I'll stick it on axle stands and do it that way, having trouble getting it onto a ramp.
Remember and let the cable adjustment fully off before you adjust the hand brake shoes, finally adjusting the cable.