Yes you can convert it to gasoline. If the engine has a bushed connecting rod, then you'll need to run a 20:1 to 25:1 fuel to oil ratio, using a good quality synthetic oil (much less carbon buildup). You will need to use a Walbro carb on it so that may require an adapter for it. You can get CH Ignitions or RCexl ignitiopn systems to use on it. This will entail drilling a hole for the magnet and gluing it in, and mounting the timing sensor in some fashion.  But other than that, it is no big deal converting one over to gas spark ignition. Just use regular grade gasoline in the fuel.

Now then some guys do convert their glow engines to use spark ignition and they still run glow fuel, so that is a viable solution too. In this case you could continue to use the stock glow carburetor on the engine. But with gasoline you have to convert over to a carburetor that can handle the more lean air/fuel mixture that gasoline requires.