I have an original 23D Cooper S dissy that I have had checked on a dissy machine and the advance curve is all over the place.

I have a 43D/45D modded (by Aldon) distributor that goes really well in my car.

Is it possible to swap the shaft, complete with the weights and springs from the Aldon to the original 23D.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Swapping shaft from 45D into a 25D might be possible, but quite involved as there are a number of differences between them.

When you say 'advance curve all over the place' if this is scatter then chances are the bushes in the 23D are worn and putting another shaft in won't help.

If it is just incorrect advance curve then replacing or adjusting the advance springs in the 23D is possible. Main point to check is the total mech advance in the 23D likely to be 15x2 deg, so needs very light primary spring and go easy on the static advance.

Yes, I realise would need to fiddle with the springs to correct the curve in the 23D4. The bushes in the 23D4 are OK. The distributor curve was professionally checked on a test unit off the car.

What got me thinking was that I noticed that a 25D shaft assembly appears identical to the 23D4. So if the 45D assembly was also identical I could just swap it over. The 45D I have is a "modern"unit that I know suits my motor.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Having pulled both dizzy types apart I think you will find they won't fit.
Totally different assembly.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I would send the 23d off to graeme russell to have it recurved / modfied. Put an electronic module in it or wire in one of those black boxes with a programable curve