Hi Hubie
Muskrat put it down as it should be, but I know sometimes if you haven't done something before it's hard to follow.
Shims have to go between surfaces that do not move in relation to each other, in this case between the drive side crank web and the drive side bearing.
assemble the crank with the driveside bearing on it, fit it into the crankcases and bolt them up with at least four of the studs so its pulled up tight and square.
Set up a dial gauge at the driveside end of the crank.
Push the crank through the cases towards the timing side.
Adjust the dial gauge onto the driveside end of the crank.
now push the crank through to the driveside and record the reading on the dial gauge
If you have no dial gauge you will need to use a vernier, possible fixed sonmehow
whatever you use repeat the exercise a number of times and record the reading each time, if the readings vary (which they might but not by much) work out an average or take the most consistent which ever your happiest with.
Now you have the end float, when shimmed and assembled you need to aim to have a max of 3 thou so take 1 or two thou off your measured end float and fit this thickness of shimming between the bearing and the crank web (fewer thicker shims are better than many thin ones).
Can be a bit of a bind as you don't want to be removing the bearing more than necessary, so take time measuring.
I've done this twice once with a vernier and the last time with a dial gauge (much easier) managed to get 1.5 and 1 thou respectively
Good luck