In my impalas I install 71 Cadillac Fleetwood coil springs up front and take the front ones out and install them in rear. Chevy truck springs are shorter than car springs. Ford truck springs will work if you have access to any. To switch springs you got three options, you can use a aggravating coil spring compressor ,#2- jack up car , block up front and use a tractor front bucket sitting on front fenders and a floor jack to compress springs and ease off jack , repeat to install or #3- like I do , I use the car lift with a idiot stick under rear of car (to prevent lifting car off of lift)and a hydraulic transmission jack under control arm and jack her up -take loose and let her down and remove spring - repeat back in.
Does your 84 have a carb? If it has carb ,it will have a engine mounted fuel pump. A carb only requires 5 PSI to operate correctly. You might have another problem. If it is TBI,try a inline electric pump for a Ford Bronco with TBI. I was thinking that TBI didn't start until 85-86.