The 43cc (2.60) engine with canister will turn a 24x10 prop @ 6100 rpm for 30+ lbs thrust
The 35cc with 3271 muffler and 20x10 prop will run at about 6400 rpm and about 18-19 lbs thrust. 7300 with tuned pipe and 24 lbs thrust
For 3D you need at least 1.5 times the plane weight, but 2 times the weight is better, so between the two, I would prefer the 43cc engine, which has a bit of power to spare for exhaust experiments.