and where do you get that info?
The iPhone 3Gs has an ARM type 7 CPU. It is the first iDevice to have one, with the iPod Touch 2G being the last type 6. Apple no longer includes the type 6 instruction set. Similar to how Snow Leopard no longer works on PPC Macs. The iPhone 3Gs was also the first iDevice to have the PowerVR SGX535 GPU. The iPod Touch 2G was the last to have the PowerVR MBX Lite 3D. The driver kext is no longer in the firmware and its doubtful that the 4.2.1 one would work.
Furthermore, Apple doesn't sign the soft SHSH for 4.3 and none of the jailbreaking tools out support it. So unless the OP wrote his own method for jailbreaking 4.3 and getting around the soft SHSH, he has just faked his firmware and build number.