This is the calculator I use to make this quick and easy.
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

There’s not much difference in RPM @ 50 mph between the 3.55 and 3.38. About 100 rpm in your case: ~2100 for the 3.38 and ~2200 for the 3.55.

However, either of those options drop the RPM significantly from your current 4.11 rear. It should take about 2550 rpm to get 50 mph there.

(By the way, I’m using 26.9 inches for your tire size).

1951 3100