[dave295]

A Ford Toploader is a great gearbox, being a bit stronger than a single rail.
A Single rail was used in the XC Falcon Cobra. That's a big heavy car with a 351C.
A single rail was also used in the Ford Cortina with a 250ci engine. This gearbox has a shorter extension housing on it as the car is smaller than a Falcon.
The gear shifter is screwed into the top of the rear of the ext. housing. This may give you a better stick position in your car in relation to your seat.
Plus you can always bend the gearstick with an oxy to suit you and your car.
The Toploader has external linkages which may cause clearance issues with your transmission tunnel during usage and servicing.
A single rail could be sourced from an old XD 250ci etc. fairly cheaply (you'll need another bellhousing to suit the V8).
As a side point I picked up a single rail (sans bellhousing) a week or so ago from the Darwin dump shop for $10.00 a week ago.

A lot of the Cobra's built in the sixties had a V8, a four speed and a Jag rear end.