I ordered my springs from Jegs. QA1 10" 250 in/lb springs. Here is a link to a 10" 275lb QA1 spring. To find different spring rates just change the last 3 digits of the part number. http://www.jegs.com/i/QA1/122/10-275/10002/-1
I also ordered Coleman Racing adjustable sleeves from Jegs. It was cheaper to order them from Jegs than from Coleman due to free shipping from Jegs.
I've got a pair that I built myself using Sensa Trac struts, 250# QA1 springs, and the Coleman Racing sleeves/adjusting collars. They were probably on my '87 GT for less than 5000miles. They worked fine. I took them off 'cause I built a new pair using red Koni struts and 300# QA1 springs. I'll post some images later if your interested in buying them. If you PM your cell phone number or email address I can send the images using my cell phone. Thanks, Ray in TX.
I think 250lb springs would have been perfect for a sporty daily driver if my car had a 2.8. I do wish I went with a slightly higher rate though (275 maybe) because of the extra weight of my 3.4 dohc. That said, it does ride pretty well and definitely performs better than the stock set up. It's probably close enough that I'll never actually bother changing it.
My plans exactly. Nicest thing is when I do my motor swap (3800 or LS, undetermined), I can simply put in a heavier spring. But thats a year+ down the road. Gotta get it safe with the 2.8 for now for work.
[This message has been edited by EvilSqueezles (edited 07-30-2013).]