I thought you were serious until you wrote, "Im also considering on putting vents in the firewall to blow hot air into the cab".
There is a reason they call it a fire-wall.
You will read everywhere that pusher fans do not work as well as fans pulling from behind the radiator. GM doesn't seem to agree with that.
My '87 Vette has an auxilary pusher fan directly in front of the regular fan. It was optional or standard on Z51 optioned cars.
My '67 292 has the original 4-blade fan and no shroud. When I installed the AC I simple added an electric pusher fan that came from a '94 Cadillac deVille.
Look in the wrecking yards. You will find everything from Mercedes to mid '80s GMs with pusher fans.
