I would go with the 3W 55i. Rear carb, I don't think you would cook it if you leave allot of exit area for the air and don't cut all the front opening of the cowl out. Just enough to let air into the engine.

From what I have gathered its 1-3 ratio for intake area vs area for exit air, or about.

Plus lots a room in that bird for a in cowl muffler, nothing sticking out but pipes I would think.

A simpler setup would be a G62, they are very reliable, and I would get one with electronic ignition, they do start better.

I had one with the magneto, it could be stubborn at times. Plus you have to slap the prop hard to get a good spark, and it could kick back if ya did not slap it just right. [&:]