Add-a-leafs, lift blocks and U-bolts for 1988-98 Chevy C/K 2500/3500 trucks can be swapped in for the rear. Shock extensions for the same Chevy vehicles work as well. All are found on eBay for pretty cheap.
As far as your fronts are concerned, you may be SOL on that. You are pushing that front A-arm geometry too far with a 3" coil lift. 2" is the highest you should go. That's why Boulder & Weldtec only go that high on their coil lifts. When I used my MCBay undercoil spacers, I only went up about 1.5-1.75" to play it safe. You are going to run into issues, not only for ball joints and upper control arms, but your shocks aren't going to be settling into their correct position for valving. This is why your front suspension feels horrible; it's in the wrong part of the travel. The front shock is part of the limiting factor for length of travel for your suspension in stock form; It is a stress member with regards to droop. In regards to doing a coil spring lift you are sacrificing downward travel to achieve your lift. As a result, your shock with respect to valving and travel are at odds, and the result will be a stiff ride on the front. This is the same issue that leveling trucks have. Also, don't rule out that your stock shocks may be old/shot.
WeldTec is your only option for Fox shocks or hit up Boulder Offroad for the Bilsteins, as far as off the shelf goes; and those will be for their 2" coil lifts. And as far as I know, they are stock length shocks on the front. Outside of that, you will have to measure your full extended length and full compressed length (travel) to figure out a shock to fit those dimensions, and hope you find something with the correct valving and correct mounts. Probably something along the lines of a truck or suburban.
On the rear you can utilize up to 1" of lift on stock shocks, but past that you will need either extensions (poor mans way) or new shocks (measure or go to the professionals like WeldTec and Boulder).
I utilized Ridetech Fox shocks on mine (ebay at a smoking deal). Way better than stock, but probably not as plush as WeldTec. But for my purposes of towing, they were perfect. They still are available on eBay, but are now rather pricey. Hate saying it but you would be better saving up and doing it right. My lift was mild at 1.75" front and 1" rear on 2017 3500. But I will be doing a spindle lift on the front next year and larger blocks in the rear with extensions.
