Originally Posted by pierce

to switch a freewheel from 7 to 8, you might need to shift the axle some and swap the spacers around so there is more room on the drive side for an extra gear. and you'll need to redish the wheel after doing that. I swapped my old stumpjumper rear wheel from 5 to 7 speed when the original suntour freewheel finally wore out. its wheel was symetrically spoked (0 dish) originally, the rim had to move over about 1/4" relative to the hub so that the brakes stayed centered and there were room for 2 more gears

(semi-ignore my previous comment, I forgot you were switching to road brifters).