[Jeff Chambers]

Depends on a lot of factors. If your heads have had a valve job(s), then the valves are set into the seats further and shimming will be required to get consistent seat pressure. Other things that you'd have to know include length of valve stem (some factory valves had anti-rotation devices that affect spring height, desired seat/open pressure, coil bind height, etc.

If you're not sure, then I'd really recommend pulling the heads and taking them to a reputable machine shop. The shop will have the specialized equipment needed to measure the installed height, check for coil bind, etc. Personally, I'd never do a spring swap with the heads on the car unless it was an absolute emergency. I like to have everything absolutely correct (seat pressure, locks, etc.).