[mr48chev]

Three very good questions there.

I've seen aftermarket suspensions that don't have much for an upper spring seat The spring just sits on flat metal around a steel ring if it even has the ring.

If the spring on one side isn't seated right in the pocket it might cause the truck to sit high on that side. If you can get under the front with the wheels on the shop floor measure from the lower control arm on each side to a spot on the upper spring pocket to see if there is a difference. you can probably turn the wheels this way and that way to do it.

If the truck has been clipped/subframed and they didn't get it on square they may have cut one spring a bit to compensate. One of my buddies had to cut a guys Subframed truck's frame up and start over with a replacement frame and subframe once because The subframe that was on it was either put on wrong or bent before it was put on. The owner didn't know the history of the truck as he had bought it that way and it always sat a bit cockeyed.

Were there any rubber spacers on top of the old springs? We used to call them air conditioner spacers when I was doing front end work but I used them a lot to level up cars that weren't quite level side to side and those were pretty new Pontiacs at the time. If it is a subframe or S 10 frame there could be a spacer stuck in the upper spring pocket on one side that was put there to compensate for a weak spring before. They usually fall out when the spring comes out but someone could have used some kind of adhesive to put one in with.

If you stand the old springs side by side are they close enough to the same height?

Did the new springs come in one box together or did they come in separate boxes? Separate boxes I'd check for parts numbers on the boxes and even in the same box I would check to see if maybe the springs had tags on them with parts numbers. You may have ended up with springs that aren't the same weight rating.

Is the air pressure correct on ALL FOUR CORNERS? low or high pressure in one of the back tires can throw things off on the front especially if the truck has been sitting in the shop for several months. You might have a slow not very noticeable leak in a back tire that has thrown things off at the front. Years ago I actually had a rear tire on a car go flat while I was aligning the front end on the rack. I'd check the gauge and it would read one thing, check it again without making a change and it changed. One of the other mechanics hollered out, "hey you know you got a flat rear tire"? The car owner must have picked up a nail on the way to the dealership.

Are the spindles the same drop? did you check parts numbers back to the catalog to see if maybe one has a different drop?