I did not think there was a deck height difference for any of the 1275 blocks. That was only the case for the 970 and 1071 S blocks. These required different piston pin to crown height to account for the different rod/stroke ratio, if i recall correctly (waiting to be flamed on that one).
There were some known porosity problems with earlier A+ blocks, resulting in some of them being sleeved in all four cylinders by the factory.
Earlier 1275 A blocks had the smaller journal and later 1275, including A+ had the larger journal, which meant different rods for each, but the centres are still the same. You have a new crank, so presumably either have or will get the rods to suit.
The pistons you have on the way were designed to have plently of crown height so that you can machine the height and dish to suit the head and block combination that you have.
All in all, i think that you should get the 1275 block that is available and in good enough condition to bore to the pistons you have on the way. Bear in mind that if you are going to 73mm or above, offset boring will allow you to get further rebores to 73.5 and 74mm - and to get a block good enought to have that capacity.
We have a preference for the later 1275 A blocks here in Australia simply because there are more of them available than A+ without having to pay the Cooper S tax. But the pistons fit any of the 1275 blocks.
My engine is a 1275 A out of a Leyland 1275LS Mini, and therefore one of the later 1275 A blocks, 1978 vintage. I am using a reground large journal crank with Cooper S rods. The block was decked to ensure a flat face for the head, bored for 73mm pistons. I used Hypatec pistons, but these had the crown machined to the deck height and a small dish machined to mach the combustion chamber size in the head to get 10.9:1 compression.
Matching all this is a RE282 cam which is not available any more, but Graham has a newer cam that is similar. End result was 127hp and 113ftlb. See the dyno sheet here
http://www.ausmini.com/forums/viewtopic.php?f=5&t=44857&hilit=wakefield and more details here
http://www.ausmini.com/forums/viewtopic.php?f=5&t=31567&hilit=wakefield about what it has done on the track.
I limit to 7000rpm due to the crank material.
This engine is fantastically drivable. I took the car over to the Netherlands whilst i was living there and managed to win the class at the sprints and set fastest time of the day at the slalom on a couple of occasions.
Good luck with yours.
cheers
michael
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