you most likely won't get the needed amount of thrust with a 5x3.5 three blade
I would NOT use this small a prop on a .40 size engine. The engine will over - rev and most likely cook itself to an early demise.
5X3.5 IS the correct size for the .049 originally discussed, but NOT for these larger engines. (Therefore, I can't give you a thrust guess with this prop.)
Just so you know Ralph, "thrust" is not a number, or factor, that's used very often in RC flight. We usually talk in RPM, HP, and "torque" curves. Some folks have played around with these engines pulling against a scale of some type, but I'm not one of them. Sorry.
Dennis-