Core 2 Duo P7350 2GHz, 1066 MHz FSB, 45 nm VID Voltage Range 1.062V-1.150V
Core 2 Duo T9900 3.06 GHz, 1066 MHz FSB 45 nm VID Voltage Range: 1.050V-1.2125V
Im a bit worried about that difference in VID Voltage. No easy way to tell if your motherboard will support that. My guess is the motherboard compatibility will be OK.
Cooling for the more powerful CPU is where I think you'd run into a problem.