[SCOTI]

Yes, bags can be substituted for the front coils on a '94 truck. The OBS set-up does not use the bolt-on upper x-member plate like the earlier (Squarebody & before) trucks did. They use a stepped lower plate & spaced-out upper bracket that fits within the coil spring hole in the frame & are secured on top w/a stud that's located where the original upper shock mount is.

An air-over-leaf set-up would work in the back but will require more than one leaf if it's to get used as a truck. Unless he puts in a step-notch & cuts out the bed floor, the single-leaf/helper AoL set-up isn't going to yield much for the effort. A flip kit yields around 8" of rear drop & the frame rail + bed floor already limits travel @ the point.

This image is a front bag set-up for an OBS truck. You still need to attach a shock to the lower control arm like the 63-87 style trucks.....