on traction bars, only the ones connected to something at BOTH ends will possibly help with brake wheel hop.
with the block between the axle and springs the force developed when the brakes are applied is multiplied because of the lever action of the spacer block. if the springs are old they will wave easier. rather than install new springs you could install the traction bar idea instead. new springs will need to be "set" so the ride height is going to change after a bit as they break in to being used. I would say with the coil springs over the shocks that who ever set up the rear suspension was having trouble getting the ride height they wanted. one more leaf in the rear spring pack must have been to high and then without it the truck sat lower then desired, that's why the coil springs were added. personally I'm not a fan of the coils because they put a lot of necessary strain on the shock mounts. I would rather dial in the proper springs and/or shackles/blocks etc.
one other thing to check, since the suspension has been altered, is the driveline angles. the output of the trans needs to be roughly the same but opposite of the pinion on the rear axle. usually 3 deg down on the engine, because that's what the factory used so intake manifolds and oil pans/pick up tubes etc are made so the carb sits level on the intake when the engine is in the chassis. so, 3 deg down on the engine and trans would mean 3 deg up on the pinion. having an adjustable length traction bar set up will also keep the diff from turning under acceleration so the set pinion angle will stay ,more like what it should be. with the blocks installed and no traction bar the pinion angle will change easier, just like it does under braking. something like I posted in post 12 above will help keep the angles correct under accell or braking. without buying a new set of springs. you can easily fab one of your own but maybe check for a prefab one first because the threaded tubing and tube ends add up fast.
these guys have lots of misc brackets and kits for things. they are Canadian dollars so USD goes further.
https://welderseries.com/?_vsrefdom=...EaApWuEALw_wcB