I guess he means after spark ignition conversion..

well, accurate metering of gas is possible but could be hard with stock carbs.

If the needles on the stock carb are very fine threaded, its possible to run gas with the stock carb.

As gas needs alot more oxygen to burn properly, the needle will be very sensitive and leaned out. (like the 0% nitro fuel compared with 30% nitro fuel)

A pump of some kind is near necessary to run gas as even the slightest change can lean out the mixture and stall the engine.