Spring rate questions?

I have Aldan Eagle adjustable shocks on all 4 corners and I am changing the spring rates because I'm going with a BBC instead of a small block. Now I will end up with an extra set of springs on the shelf. What are your thoughts for spring rates for a 30 Model A roadster? I guess I should say I am running an IFS and a parallel 4 bar on the rear. I am leaning toward 400 lb on the front with a rear of 225 lbs. I just don't want the roadster to ride like a dump truck with an unbearable ride, but I do not want something which is so soft it will not respond right with my roller BBC. Thanks ahead of time for your assistance and direction! :confused:

Front and rear weights with the BBC in place will get you real close.
Corner weights will get you closer.
Check any one of the good suspension books for spring rate ratio and do the math. That will get you even closer.

Doug

Best to put the car on a set of scales, but if they're not available you should be close on the front but IMO too heavy on the rear. Think I'd drop to around 175 or so----again, depends on the weight and weight distribution of the car....

One thing I forgot to mention is that there will always be 120 lbs in the rear rumble seat because the roadster is a 3 passenger vehicle. The ONLY times it will not be that way is when my wife and son are not with me which is very seldom. I'm not exactly sure how much this weight will affect the spring rate.