I am changing the seats in my 1990 from the original power seats to manual and in need of manual seat rails does anyone have these for sale.

As far as I know from 1987 up all drivers seats were power and a power passenger seat was optional and yet something like only 10% were sold with the standard manual passenger seat. You might try some online Corvette salvage yards for some early C4 manual seat tracks/rails, since they were rare even in early C4s I doubt you'll have much luck though since the manual rails were "rare". Further I'm not sure if early C4 seat rails will work in a 1990. If you're handy with fabrication/modification you may be able to use the manual rails from another model car??  I don't know if it's still true but "reman" power seat tracks used to still be available from some of the vendors here on this forum.

my seats work perfectly but my wife doesn't like the high lower seat bolsters which contain all sorts of button controls so i purchased a set of Z06 seats to replace them. i want to keep all my original seat components together in case i ever want to sell.