I used a Mk 2 Ford Escort rack - standard one is 2.9 turns lock to lock, but you can go as low as 2.4. I took out the original power rack, having measured where it sat in relation to the subframe. i made a subframe for the rack

from 3mm steel plate with tube uprights to fit into the holes where the original rack bolted up, then added clamps to hold the rack in place. To suit my M42 exhaust manifold I offset the rack by about 40mm and added a 40mm extension to one side of the rack (readily available in pairs from folk like Rally Design)

The steering column extension was a combination of original E21 and Ford Cortina
With the whole lot bolted up it worked beautifully and smoothly, with only one problem - turn the steering wheel right and the wheels went left
Once I figured what I'd done wrong
I wont be able to get photos of the rack fitted, unfortunately, as the car has gone into storage while we move house
Neil