No need to upgrade to 2.4 simply because of a gas engine. While there's nothing wrong with 2.4, it'd be hard to use "I'm running a gas engine" as justification for that expense if you're happy with your current setup.

Simple precautions are all that are necessary. The philosophy is this: Don't "transmit" rf interference to the back of the plane with metal. Metal typically means: Ignition switch harnesses and throttle pushrods. So...

1. Mount your ingition switch up ahead of the firewall.
2. Use plastic for your throttle pushrod.
3. Philosophy: No wiring (or other metal) should "bridge the gap" across your firewall. Try for 12" separation if you can, but I've run less without issues.

I use a 9cap futaba, and have flown several gas powered airplanes without problems this way.
As with glow, avoid metal-rattling scenarios with control surfaces and the like.
Do a thorough range check, and this will instill confidence that all is well.