Today we have added Complete dual CPU core processor trays featuring Two Quad Core CPU's for the Mac Pro 2009 version 4,1. These are a great upgrade to any quad core Mac Pro.
For the adventures these can be used (with some DIY no how) to upgrade your machine to a 12 core super computing beast.
You will need to update your firmware as discussed here https://forums.macrumors.com/threads/upgrade-mac-pro-4-1-to-5-1-efi.1894850/
You can then install new CPU's as outlined here
Two notes, First we assume no responsibility in damaged caused by trying an upgrade and second......Go with the D lidded CPU's, here at Part haven we find that we can successfully de lid a CPU 2 out 3 times successfully. Ruining a CPU is far cheaper than ruining a CPU Tray socket.