I put suspension techniques lowering springs on back in 1998. Now I'm slamming off everything. It's brutal. Took some measurements and found the front at 25" and the rear 26. I want to go up a bit but not to factory height. Would Sportlines or UMI's do the trick? What would you folks suggest?

 

At that height it probably looks pretty good but for your average street car that's a bit to low and your steering geometry is all fudged up. Are you measuring from the ground to the fender lip? Is this was this a daily driven car since '98? Suspension Technique wasn't exactly top of the line back in the day, you get what you paid for but I wouldn't really expect any after market springs to retain their shape memory after a quarter century. As for your question of how much sag would you say 24 year old springs have? There's to many variables Spring material, Spring manufacturing, average road conditions, condition of other suspension components IE control arm bushings and shocks and struts, ect...
With off the shelf aftermarket lower springs there's the chance that after you install them they may not be exactly what you want, some people get what the manufacture claims what the drop should be and some don't, again there are variables. If it's in the budget I'd recommend a set of UMI or Ground Control weight jacks, they are pricey at $6-700 dollars for a whole set but you can adjust height to where you want the car to sit and you can use a different spring rates. Price wise the next option cheap would be the Sportlines or UMI's, chances are you get them in and you be happy with the results, but there is a chance that you may not, I'd would say probably 75/25%. The cheapest option would be to get a set of factory replacement springs and cut them to the height that you want, this option will take more time to get them right cause you have to install them get some measurements then cut them in a manner that wont add a bunch of heat to the springs IE plasma torch, they need to be cut with a cut off wheel or even a hack saw, the adage of measure 2 twice cut once surely applies.
Even if you get the higher end weight jacks, if your shocks and struts are in the same condition as your current springs, old AF, replacing your springs is just a band aid that's gonna fail in time, the two most important components in the suspension are the tires, shock and struts. Koni is pretty much the gold standard these cars, pricey but you get what you pay for and their rebuildable, there are others like QA1 and Viking but KONI's are commonly used in street and racing applications, KYB is a distant second not really close to KONI but a way better option than factory replacements, then you have your factory replacements. Something to keep in mind is you go with the weight jacks and they'll have a heavier spring rate a factory replacement strut is gonna fail sooner than later.

 

I actually went with Eibach Pro-kit and KYB AGX shocks and I'm pretty happy. Rides nice. They were a little high after install but after a couple of hundred kilometers they seem to be settling in. There's just under a fist height between the tire and the fender lip.