Many have converted glow engines to gas. In general, rods don't need any modification. The FG-14 appears to use the same rod as the FA-82. Lubrication is tricky but using it seems that 12:1-22:1 oil ratios will be suitable. Just follow the ignition's installation manual to install the ignition. You can make some changes to ignition to find the optimum setting once the engine is tuned well. If the carb is oversize you might find it doesn't draw fuel well when running gasoline. It will be very sensitive on needle settings, Just be patient and use a systematic approach to find the correct needle settings.

Here's a good thread.

http://www.rcuniverse.com/forum/m_7282593/tm.htm

The Saito prop hubs are collet type so it's easy to change timing.