The gas carburetion is a problem with the regular glow carb.

A very old man at my club has been converting the OS 70 and 120 for years, playing with the inner diameter of the carb tubes inltes, finally he used the Irvine .40 carbs and they are just perfect from stock, with no mods at all.

So if you want to try, I strictly recomend to use one of those carburetors.

Adapating a walbro could be a chance, but they need a lot of clearance with the firewall and an adaptor ...also crank pressure outlet to the carb...

Tell us later what you decide.
Tato Lazo.