Thanks for all the great info guys, I will look into the face plating & side cover mods as suggested. I'm not really sure what mods have been done to the transmission so I might just have to open it up when it arrives & have a look, the description I got was "McCandless' process took this a step further by replacing the face teeth entirely with components of their own design along with special sliders" He did however give me the gear ratio, 3.04 first, and 1.88 second, 1.36 third gear, forth gear is 1 to 1, nickel alloy gears all built in his shop.
I'm trying to build a period correct Pro Stock car as it would have been built in the early '70s with as many genuine parts as I can, was going to use my '70 Barracuda but will probably leave it as a street car & buy a '72 Cuda or '73 Duster roller, hopefully an old race car. Once again thanks for all the input & I'll probably ask more questions once I have researched the Liberty modifications.
As a side note my dual plug heads came off Lauren Zeedyk's Pro Stock Volare that Lauren & Joe Liberty used as a test mule for the early Libery 4-speeds.
The maintaince is unbelievable,especially the imput shaft at 4th gear.Forget about down shifting.The crash box were designed for race only and a crude design.You would be better off with some of the newer after market clutchless trans available.With every tooth cut from the gear at the lock in position and slide collar as well as the elimination of the syncro rings use of this trans can get costly. 
The slick shifted gears are very unforgiving, and wear out quick with the untrained driver, miss one shift and take the tranny aprt to fix the burred up gear and slider 
The Pro Shifted parts are a lot easier to make shift and last a lot longer,(80+ runs compared to 40 or less runs on the slick shifted parts with the same driver and clutch 
