Sorry this will be a little long, but good info.
I recently got rid of my '79 GMC K15. It had an old Rancho 4" lift when I got it and it rode like total sh*t. When I did the 3/4 ton axle swap, I switched to Tuff Country 4" EZ ride front springs and their 8000 series shocks. Out back, I got rid if the add a leaf and used a 4" block. I also added ORD's greaseable front shackles and their sway bar disconnect. For a leaf spring truck of it's age, it rode pretty good. The softest of my square body trucks. I think one the the biggest help for the front ride on our trucks is the sway bar disconnect. It allows the front sway bar to work independent of the axle like most passenger cars. I found that the swap bar attachment point on GM lifted truck creates a binding point for the suspension. I discovered this when I tried to add a sway bar drop bracket on the below mentioned K5. When I tried to level the sway bar, I could not get things to line up unless I forced the springs to move. I then realized the springs and sway bar were working off different arcs.
I've also used a Sky Jacker 6" soft ride on a '77 K5 with their brand hydrualic shocks (circa 1991). It had a 3/4 ton axle swap on that too with 36" Dick Cepek radials. That was a full spring truck, but I felt it was a little bouncy. That could have been due to the springs, short wheel base or the 36" radials. The other truck I lifted was an '87 GMC K20. It was a 4" Rancho soft ride (circa 1989) with their brando shocks. I don't recall of that had gas shocks or not. If was a quad shock set up in front. I had a 2 " add a leaf in back with a 2" block. That truck rode like sh*t too.
On my '85 K30 I'm going to run a 4" Tuff Country HD lift due to the 454 and rear 4" blocks.
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