Re old 1940s range: Are you certain that is is presently set up for natural gas? You said there was no pressure regulator. Natural gas ranges have regulators, LP gas ranges do not. (when a range is converted to LP gas from natural, the regulator is "converted" too, meaning it is blocked open, no longer functioning as a regulator) The gas pressure is reduced by the regulator at the tank, feeding the same pressure throughout the system.
If you have adjustable orifice hoods, check to see if they are tightened down or not. If they aren't tightened, you have a range set up for natural gas. If they are, it's been converted to some other fuel gas, usually LP (propane). Inside the orifice hoods, there are 3, sometimes 4 "fingers" which, in the normal, uncompressed state, allow gas to flow through them, making the effective orifice size the hole at the end of the hood. When the hood is tightened down onto the "fingers" , they are squeezed together, and now the effective orifice size is the tiny opening between them. Tighten down the hoods for all the burners, close the top burner pilot adjusting valve completely (which shuts off the gas flow to the top burner pilot(s). There should be a similar hood for the oven burner - do the same to it. Then, adjust the air shutters on the burner venturi tubes for the best flame. It should be blue, defined, (not lazy looking and yellow) but not noisy and harsh. These are somewhat ambiguous terms, but the experienced eye can discern these features. Note that with LP gas, it is sometimes impossible to get rid of the last little bit of yellow tips at the end of the flame without making the flame harsh. Just get it the best that you can in that case. The pilot for the oven will be way too big at this point - adjust its size with the valve that feeds the oven pilot line. There's no air adjustment on pilots usually. BTW, the oven pilot is necessary for the oven to operate. Old ranges have several different types of pilot verification systems, but it is most likely a thermocouple type.
Now, if you don't have adjustable orifice hoods, it gets more complicated, but still doable. Let's assume you have a range set up for natural gas. Remove the orifices, keeping track of which ones go where. Measure the diameter of the openings (orifice size), using small drill bits for gauges. A well-stocked hardware store should have number and letter drill sizes in addition to the more common fractional sizes. Find a chart that lists gas type/pressure/orifice size/BTU. Like this:
https://goo.gl/images/dJ1TSw You'll need to assume a gas supply pressure, usually municipal gas systems are around 3.5" w.c. The chart will tell you approximately what BTU rating the individual burners are according to the orifice size. Since you want to convert the burners to burn LP gas, the orifices must be smaller, since LP is regulated to around 10" w.c. pressure. The difference in pressures are due to different fuel gas flame propagation velocities (an interesting but unnecessary topic for another time). Use the chart to find the orifice size that gives you the desired BTU output for LP gas at the line pressure the tank regulator gives you. You must either make some assumptions about this, or use a manometer to measure the actual pressure.
You'll need to braze the orifices shut, then re-drill them to the desired size. Use either Brass brazing rod or silver solder (which is actually brazing). Do not use regular tin/lead solder - it will melt out. I have spent 40+ years in the appliance repair field and have done this a few times. Done carefully, it works well. Good luck!
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