ok,
My std AVO coilover as supplied with springs are 300lb 9" long FRONT, 200lb 12" long rear.
I am going to put slightly harder on the rear, as I find them a little soft.
I would phone AVO on 01604 708101.
Avo do some dedicated track stuff and are very good, MR Mike Rainbird uses them, he of R&B Motorsport, so he would be able to give you better advice.
tabetha