Need some help, I'm building a 40 chev coupe, BBC 427, 6-71, all steel body. I have a straight axle under the front and want to use coils in the rear with regular shocks. I found a kit that will use a coil spring, 2.5 ID, sets on top of the housing and the top bracket mounts to my 2x4 box frame. I was thinking 12 in spring with a 200 lb rating. Do you think that would be a good starting point? I wish I had scales but I don't.