Mr Super Sabre, thanks for your input.

You are correct with the 4.56 ratio.....

All australian made vehicles that are column shifts ,the shifter is on the left hand side (right hand drive vehicles.)

Fseries trucks that where partially assembled in USA (FOR EXPORT) once they arrived at the ford plant here, they would have the above mentioned column/shifter installed.

So i would really need to find a fseries truck here in australia that has these , for it to be a donor for my 350.

Regarding the import of mustangs and other classic vehicles into Australia.......any vehicle with a manufacture date after 1988 must be converted to Right hand drive (costly) where as vehicles pre 1988 can remain Left hand drive but must meet a number of design criteria (australian standards) depending on age. ie a 1970 vehicle will not need to meet as many design rules as would a vehicle say 1975....
Any LHD vehicle imported into Australia (with build date after 1988) MUST be converted to RHD. very costly.......very.....the companies whom do the conversions have a monopoly......so therefore charge a ridicolous amount of money to have such a vehicle conform to australian standards......

Well after more research , i am more incline towards keeping my steering column as is.............removing the 4 speed............perhaps a lockar automatic shifter......to a C4.

My only concern here would be does a c4 bolt straight onto the 300ci?
And which C4 from which vehicle/year would be a direct bolt in fit.?
Also, would changing the gears in the diff help at all with the truck screaming at the moment? Or is it just the nature of the 300ci engine?

Oh, i dont intend to carry heavy loads on this thing, but i do want to go on the highway at 62mph without the truck screaming.