The problem with that burner, IIRC, is that there is no way to move the jet in and out or position it better. You can adjust the air draw with a sliding sleeve, but that usually won't make it hotter. Give that a try if you want.
I believe the jet on that one is just a hole in the manifold that is roughly centered over the venturi pipe ( downward tube). Done right, like on the NC forges, it is a good system.
A much better system uses a MIG tip (usually a .030" tip) to set the gas jet size and get good injection. These are screwed in the end of a movable tube ( 1/8" pipe nipple) and that is slid in and out to find the venturi sweet spot. Look at some Venturi Burner built links and you will see how that works.
To modify the burner you have for a MIG tip injector wouldn't be too hard. You would need to drill holes centered over the burner tube, and weld collars with set screws that fit the 1/8" pipe over these holes. Put a plug the existing gas inlet hole. Put a "Y" adapter in the gas hose end and add two short hoses to connect to the new burners. Put a gas hose connector with a needle valve on the end of each 1/8" gas injector tube. Put the gas injectors in the collars and hook the gas to them. Turn on the gas at 5PSI and crack ONLY ONE needle valve. Light the burner inside the forge, and slip the injector tube in and out until it runs smooth. Increase the needle valve and regulator setting until it starts to blow out ( it may runs as high as 15PSI). Back off a tad and re-adjust the injector and needle valve for max efficiency. Repeat the adjustment until it runs smooth at all pressures from a coughing flame out ( low) to a sputtering blow out ( high). Lock the set screw down tight when it seems right. Shut the needle valve and repeat with the other burner. Each burner can now be separately adjusted by its needle valve to have even heat in the forge, and the main gas regulator can be used to increase or decrease the temperature.
If that works well, you can turn that forge on its side (I haven't done this, but heard it helps). That way the flames don't blow directly on the blade. You should weld on some sort of brace for the burner so it doesn't bend or break off. Build up the corners of the forge chamber with satanite in to make a more tubular chamber shape ( sort of octagonal with rounded corners). That will get a little swirl to the flames.
Finally, use some fire brick to close down the back and make a smaller front entrance ( 3X2"). These can be changed as needed for long stock or wide things.
