Re: front coilover springs
Coilovers will work but they aren't really worth the money. Chances are he can buy new springs for far less.
Anyway, I'd jack it up and measure the coil diameter and the height of the spring along with the width of the spring. I'd then see if a heavier model truck than his has a longer spring. Or his springs could just be wore out. It does happen.
You could look into other model springs but then you'd have to know the spring rate as well as all the dimensions I already mentioned. One of the "cheap" ways of lifting a Bronco II is to put F150 springs in it but it makes for a rather rough ride.
I'd avoid coil spacers, in many states they're illegal anyway.