Jerry, I’m not trying to make the truck for racing mainly going on a cruise on the weekend.
Other option on transmission I have been looking at is a 3 speed manual transmission with over drive but looking at the cost of it all going open drive line swapping out rear for gear ratio to be 3.90 will it be better to just up grade gears in the rear end to 3.90 stock ?
I did the open drive conversion and have over 100,000 miles on my set up. My truck is a '49 with a '56 235, '69 3sp+od, 1949 rear axle housing, 1949 axles, '57 3.90 differential (plugs right in), and of course an open driveshaft made to fit. On a recent 1000 mile+ round trip I averaged 17.8 mpg.
The overdrive transmission has paid for itself by the increase in fuel mileage. About 5 years ago I installed a vacuum gauge and that has changed my shifting patterns dramatically. Formerly, I would put Overdrive to use whenever I had speed excessive of say, 60 mph. Since installation of the vacuum gauge I pay attention to optimum vacuum and NOT MY PERCEIVED SENSE OF ENGINE EFFICIENCY. I am now relying on real time data of optimal torque range as stated by HRL's post above.
