Use the +.030" 1275 thrusts, surface grind the steel backing to get what you want. I've put a few 1300 cranks into S blocks.
(And vice versa, using std thrusts surface ground approx .016" each on back).

I think the SA crankshaft center main is identical to a 1300 center main. You will need thicker washers to control end float, and an ancient Se7en Enterprises catalogue I have suggests you buy a set of +0.030” thrusts and a set of standard thrusts and mix and match to obtain the specified clearance. If you were fitting a Cooper S crank to a 1300 type block you would need very thin thrust washers, which used to be available, or can be made.

In any case, an experienced mini parts specialist can likely sort out your needs.

I 'd be interested in the out come of this effort. I have a couple of 1071 Cooper S cranks as well as a SA 1100 crank which I had ground for Cooper S 1.625 rods and to correct the stroke. After which it was heat treated and shipped to me. I was recently doing some clean up around the shop and arranged my cranks. 1 970, 2 1071, 1 SA1100 1 1275 and a pile of others less interesting. 

I'd think the crank thrust will have to be special or hand fitted. What are you planning in the way of rods? I have not made any effort to fit my SA crank to any of my Cooper S blocks. Having only one FJ block which is about .250 shorter than a common 1275 Cooper S block. I have been trying to buy a set of 6 inch rods for years. Mostly finding sets of three or less ex race rods from engines having suffered a failure. Finding a proper match is almost impossible. The new generation 6 inch rods seem to all use custom pistons and 19 mm pins. I'm all ears so come back and share what you learn, I'm interested. Steve (CTR)

Hello,

What modifications are required to fit the South African crank into a Cooper S block?