Question about suspension...

H&R seems to be a pretty good product so let's start off by assuming it's not the spring itself. It could be that one of the insulators has managed to work it's way out from under the spring. When I install springs, I usuallu tie wrap the insulator to the spring so it can't slide around the spring. The other thing I do is slightly grind the end of the spring (the point) and put a small bevel on it so that it will slide into it's pocket if it's close. Sometimes springs have a burr on them from the mfg and it can keep the end of the spring from indexing on the pocket. I would also check easy stuff, if the springs are progressively wound (so that they ride easy but provide a harsher ride as it compresses) make sure that the top is the top for both springs. Lastly, almost all garage floors are not flat, they are designed to allow water to run off. So use small 2x4's to make sure the car is actually level prior to checking the ride height, and make sure the front tires are pointed straight, turning one way or the other increases diagonal weight (sometimes called wedge if applied statically).
Hope this helps

move

Did you move the car? Back the car up atleast one full tire rotation, pull forward again and then measure again.

Also....did you take note of where the end of the coil was on the stock springs? If you didn't put the new springs in with the end of the coils at the same spot the ride will be uneven.