Compression will depend on the fuel type your B was designed for. If your intake manifold has a "boxy" looking center above the carburetor and two fuel tanks, it was designed to run on Kerosene, sometimes called "distillate" or "tractor fuel". In that case, the compression ratio was 4.7:1. Otherwise, the gas compression ratios were 5.2:1 or 5.75:1, depending on when the engine was manufactured. Just guessing, I would go with the 5.2:1 ratio and a compression test on a good cylinder would show about 100-110 PSI. A distillate engine would show about 80-90 PSI for the same test.
Hope this helps,