THM400 to 5 or 6 Speed manual swap?

[ROCKETPWR]

I have recently began the long journey of restoring a 1973 Oldsmobile 88 Royale convertible. I started out by rebuilding the engine and transmission.
The 455 Rocket, as I'm sure you know, was detuned horribly this particular year with the "J" cylinder heads and deep dish pistons. I rectified this by changing the pistons, cam and installing a set of "C" cylinder heads with headers. The engine is strong but the 3 speed automatic with the 2.73 rear gear one wheel spinner does not allow me to know it's full power. Has anyone in these forums installed a 5 or 6 speed manual transmission to a 455 Rocket engine? If so, which transmission was used and what kind of adapters, if necessary, were used? An overdrive sure would be nice. Also if anyone knows where I can find a limited slip axle for a big "B" body car, please reply. Thanks in advance for any answers!!!