Well, there arent really any solid settings, as all CPUs are different. Some will need more voltage than others, its just the way it goes. 3.4 might be a bit much for stock cooling. I have my i7 at 3.8Ghz and it still gets up to 78C in Intel Burn Test, and thats with a TRUE with 2 fans and very good case cooling.
This is reasonable guide to i7 OCing on the P6T:
Core i7 4Ghz Club & Overclocking Guide - PureOverclock Forums
Although i would NOT try for 4Ghz. i7s can overclock well, but they create alot of heat. Download Real Temp or Core Temp to monitor your temps and make sure the max doesnt go over about 85C. 100C is where damage can happen.
For voltages just remember you will want to increase the CPU voltage and the QPI voltage, i wouldnt suggest going over about 1.3 on stock cooling. Also increase the CPU PLL voltage a bit to help it. Turn off things you dont need also, and there are a few settings on the P6T that are supposed to help such as CPU Differential Amplitude.
The best thing is to gradually increase the clocks and voltage as you need it, then run Intel Burn Test, checking its stable and of course always checking your temps.