Hi!
Check this post where the topic has been discussed along the 3 past years
.
http://www.haynes.co.uk/forums/showthread.php?t=7246
Don't bother about the beginning (it was a long time ago), where they say 13'' open. Shocks absorbers on a "Book" Haynes roadster definitely need to be 14'' or 13'' + a 1'' extension, open. Closed: 9'' seems OK, but GAZ SHOCKS users (like me) have 9.5'' because their 14'' open shock only comes in 9.5"" closed.
Spring rates and lengths are in the last post (from me) of the same thread. This is a starting point, and the rate might of course be changed according to the use/weight/etc. of the car.
Hope this will help
