You will have to remove the manual steering box first. I think the manual box uses 3 sheet metal brackets to mount the box to the frame, and you only need 2 of them for PS, could be vice versa, its been a while since I converted mine. I would highly recommend trashing the flimsy factory brackets and upgrading to an aftermarket bracket. I have the BigDaddy's bracket, it is worth the $100 or so, not sure if BD is still maknig them. MORE and i think Sam's Offroad make one too.
Most likely you will need a new steering shaft when converting, or at least a coupler. The coupler to the steering box is different if you are using a CJ-7 PS box. There may be a J-truck PS box that works with CJ manual steering shaft.
When putting the pump on the engine, you might have to get rid of the smog pump. Then the belt drive will need to be addressed, either a second belt, or one longer belt. I'm not sure how the V8 Ps box gets driven. I think my I6 uses a second belt. Make sure you have the extra drive pulley on your existing engine, or you'll have to add it.
Then you'll need 2 hoses, a pressure hose and return hose. The pressure hose can be tricky depending on what fitting ports are on you pump and box. Booty-fabbing a return hose is no problem, cut the tubes on the box and pump, then hose clamp some rubber hose between.