Gilles, Thanks, I came across this old thread while searching on turbo mufflers. I will soon have a very similar setup except a '29 body (I assume your '32 is fendered?) and a 3.5 rear ratio. I am trying to get 20+ mpg using the 700R4 OD. It looks like your data indicates I can hope for about 22 mpg. My engine is a '76 350 with a Crane street cam that is just a few degrees more duration than the stock cam, but I am using 1.6 rockers. Internally the engine used a stock rebuild kit and the 882 heads with only the exhaust ports cleaned up and the 0.030 overbore and flat top pistons calculate out to about 9:1 C.R. I got maneuvered into an Edelbrock Performer-RPM manifold which may be too large but the carb is an Edelbrock 600 cfm and I will use the stock HEI ignition. So far your setup is the closest to mine I have found with actual mpg data. Thanks.

Don Shillady
Retired Scientist/teen rodder