It depends on what type of engine and carburetor yo have.
For an engine with an independent carburetor the simplest is to just drill out the main jet to a larger diameter and remove the float and needle valve.
For a B&S engine with the carb on the tank remove the tank and drill out and thread the suction tube passage to fit a 1/8" NPT hos barb and then drill out the main metering jet above it.
As for a regulator a cheap cheat is to do as others said and take the loading spring out of a BBQ grill regulator so it takes a tiny bit of vacuum to get it to open all the way.
The rest is just a matter of drilling the main jet to the right diameter and then fiddling with the main jet mixture screw to get the engine to run right on whatever gas you have.
Don't bother. Millions of people have tried and the success rate is so dismally low that it's not worth the time and money spent for what you may get for short term gains only to have a still highly questionable and overall weak battery in the end.
For every person who claims they got a good battery (lasted more than a week to several months) from desulfating a bad one they don't tell you they failed to recover and fought with 20 - 50+ others to find it!