The Classic Cruiser I was thinking of is this one. I'm not sure if it's the same one or not.
http://www2.towerhobbies.com/cgi-bin...?&I=LXRX21&P=7

Just so you know, the P-51 will be less forgiving than the Classic Cruiser. I have the P-40 and, being a low wing, it requires more dihedral to make rudder turns. So much so that it almost looks cartoonish. It would really be better with aileron control. The Classic Cruiser requires less dihedral because it has a high wing.

Yes, 4 1/3AAA batteries are what you want. You should be able to find a NiMh pack of about 120 to 150 mAh in that size.

No, the stock prop is too large and not strong enough for a TD .010. The engine should come with 2 props. A stiff grey one and a flexible, unbreakable, black one.

Do you have the old Feather 3 channel? Do you trust it? I've never seen one that operated without constant glitching.

Steve Adams makes a throttle for the .010, do a search here on RCU.