The frame and fork on the 1000 was a little higher quality than the frame and fork on the 610, as were its components. I believe (but am not sure this is true for all the years) that the frame on the 1000 was made from splined tubing. The 610 has a very good quality frame, though. The tubing for the 610 was made in-house by Miyata. The 610 may not have the sex appeal of the 1000, but it's a great bike (I have one). I'm wondering if you have the year of your bike correct, though, cause by '89 I believe it was a 618. My guess is your bike may be more like an '84 if it is a 610 (browse the catalogs). Also, as already suggested, put a post in the vintage forum and you'll get much more info than I can give you.
Last edited by sesmith; 01-05-09 at 10:08 PM.