Probably should grab the proportioning valve from the Yukon. I did the same thing and the rears will lock up especially on wet roads. Front brakes are the same.
It's not wheel cylinder stoke but brake shoe radius (long wear in to new drum size) and the weight of the extra material. 2mm is fine for a clean up cut but not for any kind or gouges from shoe rivets. Still can get drums for less than $120/pair. Back in the day shoes were ground to fit.