The best way is to swap the entire gearbox but you will need other stuff such as the crossmember and the extra wiring. I'm not up on the differences between OD and non-OD Sprints. I once helped out on an overdrive conversion on a 1500SE (Andy P.'s SE) so it won't be much different.
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Meetings take place on the 1st Wednesday of every month at The Hollies Sports & Social Club, 12 Hough Lane, Bramley, Leeds, LS13 3NE
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