you mentioned 2.5/4" drop - what means did the PO use to lower it? cut springs? Or do you perhaps already have drop spindles? Usually, if you have the 2.5 drop spindle, you should have around a 3" drop spring to go with it. Just curious the set-up (in the front) as you may be able to squeak an additional inch or so out of what you currently have before going into the $$$ setups for bags, etc (I agree with Jimmydean, not many inexpensive options left if you already have 2.5/4" setup. If you just have 2.5 drop springs without the spindles, then you may get that same additional inch or so by adding the drop spindles at this point.
As for the rear, again, depending on how the PO set the truck up - you may be able to add drop blocks (if there aren't any or replace with larger ones). But keep in mind - if you lower the rear any further, you're probably going to require a c-notch to keep the axle off the frame.
Again, all depends how it's currently set up. So,
Front: if you don't have drop spindles, recommed 2.5 or 3" spindles complemented by an appropriate coil spring. If you DO have drop spindles, then the most you'll get out of it is maybe another inch if you put in appropriate drop springs (or vice versa - i.e. if you don't have drop spindles and do have drop springs, adding the other component may help a little - but in most cases, folks don't add just one or the other, they add both the spindles and the drop springs, so if you have drop spindles, you probably also have drop springs. Not true if you just have drop springs - many add the springs without the spindles - so you can help out by adding the springs to match). But if you have both already, you're maxed out for that config I believe - next step=bags if you must go lower.
Rear: consider blocks if none there already. Because if it's dropped 4" already, next step will require frame notch, etc.
If $$$ are available, scrap it all and go with air susp. Several guys on here can be of more help with the air suspension than me. I like the way the AirRide "Strongarm" air suspension turned out on the "Trucks" tv series C10 rebuild. Looks like a quality setup to me - but strangely, I haven't seen many trucks on here that have used it. It includes a bolt-in c-notch, etc. If you're looking for HOW to do that install (or to get an idea what's involved in the set-up), I'd recommend the $19.95 Powerblock TV full series DVD (
http://www.powerblockswag.com/Trucks...hevyc10dvd.htm) so you know what you're getting into. If you've already seen the shows, don't waste your money though - the compilation DVD is exactly what you've already seen on tv, just strung together without commercials - i.e. there's no "extra" stuff that wasn't on tv. But still, it's a very cool build and I enjoyed watching it the first time on tv, and subsequently on DVD.
There are many other options available and, like I said, others will probably be much more helpful than me in the air ride department. But first, to help you out, we need to know how your truck is currently lowered, not just how much.
Oh yeah, need some PICTURES!!!!!
