[duke]

Thanks for the info. I found the Carrera technical paper last week and went through the calculations. I also bought a whole range of springs to try. A few other members sent me emails for much appreciated guidance.

I set the ride height and ground clearance, checked shock range, and then tried springs till they fit. Page 15 was a lot of help:

front weights:
Spring 1150 to 1324 1325 to 1524 pounds
Length
8" 450# 550#
9" 350# 450#
10" 275# 350#

With the big block the standard 8" 500# spring was to short at its compressed 8" length. I could compress it to get to the ride height but you lost spring movement. I then went to a 10" 350# spring and the height was perfect. Needed to compresss it slightly to install it. There was more suspension movement which should give a better ride. I am running a heavy sway bars so a softer spring should be fine.

Part Number for the springs I used were 10MB350 which are available but not in the catalog.

There are a number of spring options for the 2-1/2" ID bottom, and 3-1/2: ID top coil to try. Seems they were used on early GM cars.