Coilover rates

[jpayne]

Ok Guys whats the consensus on spring rate and length for a circuit Mk1 with cosworth 200 Block 350-400 HP
with 4 link system.
Im thinking 300-320 fronts and 180-200 Rear coils of about 250mm springs.

Can low Bilstein rear shocks be converted to use as the coilover shock? I see there are non weld on sleeves available ex UK. Are they the right length or close enough?
Cheers

JP