Yeah, the T-bone used GO-435 IIRC and teh Queen Air used a GO-480 again, IIRC. Been a long time since I've worked on either. Love the T-bone though, such a good flying airplane, and roomy, wouldn't mind a runout one and stick some aluminum small block Chevies on it and go experimental. Most of the ones still in action have the Air Stair as well. Quite a few of the remaining Queen Airs have undergone the Excalibur conversion and have the IO-720 8 cyl 400hp engines. I have grown to really like that engine, it can be pricy to maintain, but when operated properly and kindly, they hang in there.
The Travel Air came with O-360 and IO-360 Lycomings. Riley provided a turbo package with either cable control or electric control wastegates. I had the latter. Good airplane though. About as economical of a twin there is, however is not a known Ice plane. However, no geared engine, although I dont understand why all engines aren't geared, especially now with the advances in metalurgy and precision tolerance manufacturing. Props should be slowed way down. Who's the engineer? What's he most efficient speed for an aerodynamic prop? 500rpm? Problem is for one that slow, the diameter would be too big. Personally I think a 1400-2000 rpm prop would work out pretty well.