does anyone know what years/models is that the coil spring is iterchangable on a 2000 ford focus?
Go to tirerack.com and look at the suspension section for your car. There will be a list of springs. Record the manufacturer’s ID# for each spring set and then start looking at other years for your Focus. You will build a year range for your springs. The manufacturer’s ID# will exist for only one part type, so you can be sure that you have the year range right. Tirerack has sport and race springs for around $200. I’m sure that you can find OEM replacements for less on eBay or other car parts sites.
I can’t answer your question, but the source for this type of information (besides a dealer) is any large salvage yard. They have books that give interchangeability among parts. They have to know, it is their business.
It isn’t worth putting used springs on it. Too much work to swap old parts. Have you checked the price of new ones?