Mike, we had previously installed the Eibach Pro-Kit springs with Tokico Illumina II shocks about 4 years ago in my SC. For the first couple of years, it was good, decent ride and handling, a bit soft when I used Hoosier road-race radials for open-track events, but I expected that. Ended using the 'firm ride' setting about 95% of the time, the ride was that good even with 255-45 tires on the car. After about 55,000 miles, the Tokicos were pretty much whooped, especially the rears ... car was very floaty in high speed turns. So late last summerl we swapped the Konis into the rear, since they're an easy job to do in the back. Much better, but the front Tokicos were getting soft too. So this springs we did the Konis in the front, I'm pleased with the result. If I leave them set about 1 to 1-1/2 turns off full soft, it rides quite well. A bit more, the ride gets a bit stiffer, but the car handles better as well. For open-track events, they get turned up to full hard, and now they are stiff enough to handle the body lean from the grip generated by the sticky track-only tires. I had thought about trying a set of the linear rate Suspension Techniques springs in the car, maybe just the fronts, since they are stiffer than the Eibach set for our cars. Ran out of time to grab them before installing the front Konis this year however.
A few of the SCCoO members have the Bilsteins and are pleased with them, as are many of the U.S. members I've seen post on these forums. From what I've heard, the valving on the front ones might be a touch soft. You can save yourself some $$ for Bilsteins by using 2003 Mustang Cobra rear hocks bought direct from Ford, they are supplied by Bilstein, and they can be bought for about $40 US each ... they are close enough to bolt in, and they are valved for 600 lbs./in. springs for the coupes, and 500 lb. springs on the ragtops, so you can match those up with your choice of springs in the Bird. With stock springs, the Bilsteins are probably the way to go. I went with the Koni shocks mainly from having good prior experience with that brand in my Fox-body 5.0 Mustang that became a track-only car, and also because of the adjustability, for playing with them at the dragstrip and open-track events.
cheers
Ed N.