Yes the waggy springs are about 2" more lift than stock springs and are also offset 2" while being 2" longer to provide a 2" stretch if mounted one way or no stretch if mounted the other. Stretch the front for sure. Stretch the back if the axle will clear the fuel tank, I'm thinkin it won't. They'll work great sprung over with 35s and not much or maybe any cutting. Put on TJ flares to run 37s.
Waggys had high gears, will need to be regeared. He'll need 4.56 gears with 35s. That'll likely require new carriers so throw in lockers a the same time. Kurt's old jeep had 33s with 4.56 gears and it was OK, revved a little high. Was good with 35s. Then 4.88s worked good with 37s. Remember the yj has overdrive.
Get the slip yoke eliminator and cv driveshaft, its good stuff.