Thee perfect motor huh [&:]
Couple choices my friend

#1 Saito FA82
#2 YS 63FZ

Both motors are excelent choices for any 40 size plane
I personaly like the Saito better bassicly because i have one and I know what the motor can do, Mine pulls bassicly 9lbs of thrust on Cool power 30% Heli
This was taken using a digital fish scale that cost me 40 buks so i know its pretty dam accurate.
Thats hard to beat, not sure if the YS can pull that much thrust.

To your next question and also the hardest to awnser because there is so many opinions and differences.

Best 40 size 3D plane, well i could never say whats the best but i can shove you in a few good directions.

First off read alittle of this http://www.rcuniverse.com/forum/m_3326939/tm.htm This will show you what everybody else likes and dislikes.

Take a look at these 3 planes for sure.

#1 Powerline Edge 540
#2 Fliton 330 Extra 3D
#3 GP U CAN DO 3D 46

I hope this helps ya alittle [8D]

Just remember theres so many options out there its hard to go wrong