300# will be pretty damn close based on Clive's calculation, depending on rear axle weight you might go as high as 350-375

Hi Sandeep,
Why not junk the bump stop on the trailing arm and fit one on the damper? That'll have two effects:
1) The bump stop then relates specifically to the damper as it should without relying on a remote location and possible miscalculation (and zip ties!).
2) The bump stop would act as a cleaner/scrapper on the damper rod adding to the cleaning seals and minimising the possibility of ingesting dirt.
QA should be able to recommend some bumpstops.

Clive

For bumpstops go with the vw/audi marshmellow bumpstops. they are a favorite of racers because of their progressive nature. You can trip them down as needed.

http://t3.gstatic.com/images?q=tbn:d.../bumpstop3.jpg

Do you have a part number? Source at the dealer?

thanks

Sandeep, could you share which springs you ended up using? Length and lbs/inch? Thanks

Mike