Carb Spacer??

I want to put an insulating spacer under the carb on my old 390, but need the original spacer to hook up the PCV. More space is supposed to shift the torque curve lower, which is good for my heavy beast, but I wonder if

2" on a stock 390 too much. (insulator on top of the stock aluminum) Has anyone played around with 1" and 2" carb spacers, and how did your vehicle perform. Everything is stock on the 4 barrel motor.