Nothing any different really. The fasteners are larger, and you typically do not have to buy a separate engine mount. Stand offs can be easily and economically made at home out of wood dowel. Most of the ARF airframes are plenty strong enough to handle the appropriate sized gas engine if the kit was originally intended for a gasser. The Stearman should be able to handle the mounting of a 30, no problem.

The question would only have been dumb had it not been asked.