The only thing I would strongly recommend is putting the best genuine BMC baulk rings you have back in.
Put the one with the most face clearance on second gear and the worst one on fourth (as you don't, down change it).
There may be better aftermarket baulk rings now available (I believe Len read) but the UK are rubbish IMHO.
cheers Ben.

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The formula for the length of a piece of string is simple: Twice as long as from one end to the centre!

I agree with Ben. You are better off stripping some old boxes and keeping any good baulk rings to re-use in your rebuild. The ones readily available are made of some type of cheese.

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1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car

Thats the plan. From the two boxes I have stripped I have come across 5 good baulk rings, I have read that they went to sintered metal at some point and they were fairly rubbish.

I am looking to get rid of the excess parts I don't need so let me know if your after main-shafts/lay gears or casings. The gears are a but hit and miss, either they're good or terrible. Seriously considering modifying the case to take the later gear set and be done with second hand parts.