Old thread I know.
If you're installing 28" diameter tires, you shouldn't need much lift, the stock tires are 26".
So the back lif first:
I added warrior shackles to the back for 1.5" lift, Gabriel Hijacker air shocks (can help even out the weight of the steel flatbed), coil booster springs (local parts stores) and I'll be swapping out some less flat leaf springs soon. Without the leaf springs I've added 7" of lift to the back already from what I started. At least 3" higher than stock.
Now the front is different.
* You could start cutting the fender out until it fits, then get some rubber to line the wheel well.
* You could go to a self serve junkyard and start hunting for springs that fit, but are taller.
* You could get coil spring boosters, this doesn't do much to the ride, just lifts the resting point for the coil.
* You could get coil spring helpers, and stretch the coil apart. It will also stiffen the spring, roughen the ride, and actually help from bottoming out the tire.
* You could get a generic air bag kit, and get bags that are for a taller or heavier vehicle.
* You could always do a hockey puck body lift, using real hockey pucks drill holes and get longer bolts for the body to mount to the frame. This is not a fun job, but ultimately the safest option. Lifting the suspension on a vehicle above stock, via torsion bars or spring helpers, makes everything work at an angle it wasn't designed to work at. Sure it can easily handle that angle for a short time, but it will likely ware the parts down faster if kept at this angle full time.
shackles:
https://autoplicity.com/2108584-warrior-products-87up-mazda-rear-1-12in-lift-shackle
air shocks:
http://www.autoanything.com/suspension-systems/77A5839A3739463.aspx