I had a look at your dyno curve when you first posted it and find that comment a little odd. At 5500 RPM your AFR has dropped to about 13.4. That is richer than stoichiometric; but, running a little rich at high engine load typically results in slightly higher horsepower. Most engines are volumetric efficiency limited and adding a little extra fuel helps ensure that all the O2 is used up. Of course, too much is not a good thing because you lose heat in evaporating the excess fuel which starts to reduce power output.

Your dyno guy may be suffering from 'digital EFI think' where it would be easy to tweak specific cells in a fuel map to push that AFR from 13.4 up to 13.7 around 5000 RPM. I suspect the Stromberg doesn't have that ability to adjust fuel delivery at 5000 RPM wide open throttle without having some knock on effects at lower RPM. Your AFR does seem to be excessive at around 2200 RPM; but, if part throttle AFR at 2200 RPM is good then wide open throttle AFR at 2200 RPM may not be an issue.

On the matter of potential modifications to the Stromberg to improve flow, you might want to consider mapping the manifold air pressure during a dyno run. New MPX 4250AP MAP sensors are fairly inexpensive (about $35 Cdn); but, a salvaged MAP sensor from just about any car will likely fit the bill (our local pick and pull salvage yard had a flat $5 charge for any sensor pulled from a wreck). The sensors almost universally have a 0-5 volt linear output and you can usually find the slope calibrations on line. With a 5 volt power supply, an analog input data logger and the sensor you can record your actual static manifold pressure during engine operation. If your manifold pressure is running just 3 or 4 kPa below atmospheric pressure during peak RPM wide open throttle conditions there is probably nothing to be had by beating your self up fiddling around with the Strombergs.

The richness at about 2.2k showing badly on the AFR graph is mirrored slightly on the torque curve. The needles might like a bit of extra meat there but probably makes the car feel lively too. Good set of curves. Smoothing the bridge would I think reduce the atomisation at lower revs and that isn't good.

Driving the car it hits all the fuel ratios for me. Idle about 13.2, cruise 14 to 15 and full open throttle 12.5. I was going to experiment with dashpot oil as well, using 80/90 gear oil at the moment.

The idea of the porting post bridge is to make the air flow easier the same as at the front of the carb with stub stack at the entrance. It's opening up the area at the outboard side of the piston. Tapering the lower front and rear edges of the piston is suppose to improve throttle response. There definitely is extra Hp to be had with more carb.

Years ago I rounded the front of the pistons on my B16B. Didn't notice any difference. My comment about keeping the bridge sharp was because at that point the fuel is being sucked from the jet so having the smooth airflow changed to "rough" helps the atomised air in the inlet manifold. It doesn't want to drop out of atomisation onto the walls of the manifold. This can happen with the alloy manifold as it runs cooler than the cast iron one. The GT one piece is the best of all of the various one and 2 piece setups. The alloy inlet looks cool but it may be too cool at times!