With the tracks I raced on, the gearing was more about harnessing the power to accelerate rather than top speed per se, and I used to find top speed was more limited by the brick like aerodynamics. I tried a standard, non overdrive 'box, standard overdrive and a ST geared close ratio 'box. Latter was great but due to the high first, I usually lost places off the start line. The standard OD 'box gave the best race position as with a lightened flywheel, good tyres and a small twin plate clutch I could make up anything up to half a dozen places before the first corner if everything went well. That 'box has overdrive on 2, 3,and 4 gears to maximise the power out of corners (2nd OD is fine but only to select in the corner and then put the power down). Effective top speed was in 4th (not overdrive) at 7000-7500 rpm. Engine had block brace fitted.
I found the LSD was worth at least 2 seconds a lap, especially where there are slow tight corners. Those were made worse as best lap times were achieved by setting the suspension and steering geometry up for very fast corners, not the slow ones. Front and rear adjustable tie bars are fitted.
Ford axle from memory is just over half an inch narrower, but I used spacers and long M10 stds (NS380) to position the wheel in the centre of the arch to allow the largest tyres I could fit in the space (rolled arch edges, I wasn't allowed to fit bubble arch for my race series). Tyres were 195.60x14. Bigger the footprint the faster you can corner. Ford axles come with two flange sizes and the Sprint prop bolts straight onto the smaller. Bigger problem is the 4" stud pattern. After re-drilling the Ford hubs to the Sprint PCD, I ended up buying stonger half shafts with separate hubs from 3J Driveline. I waited until they made another batch of hubs and they drilled the blanks to the Sprint PCD specially for me. In hindsight, keeping the rear Ford PCD, fitting Ford PCD front hubs (using stub axles from Rob at Sprintspeed) would open up access to a wide range of wheel sizes and makes a lot of sense. Two sets perhaps, road tyres to the track and change wheels to sticky rubber just while racing? I was warned against using 40 plus year old alloys on the racetrack as the modern sticky tyres would put much higher stresses on them. The 14" ROH wheels have been fine.
We measured and photographed the Sprint axle, cut these brackets off very carefully. The after grinding the brackets off the Ford axle, we simply postioned and welded the Sprint ones on. We also had another Sprint axle so we could make doubly sure positioning was perfect. Relatively straightforward.
There are videos on YouTube (search Dolomite Sprint No 20) and some others from the series (AES) from other cars. As I'm selling the car, there are photos on https://www.trademe.co.nz/Browse/Listin ... 1505414459
Happy to answer any other queries.