I don't know how heavy your plane will be. SIG recommends five HS-625MG servos for their Extra which is around 74" wingspan and 13 pounds.

You could go with HS-925MG or HS-945MG for more torque and good speed but they are almost double the price of the 625s.
For even more $$ you could use digital servos with coreless motors.

I guess I'd contact the kit maker (if still in business) for specific servo recommendations if there's nothing in the manual.

Here's a link to the 1.60FX manual which has prop recommendations http://www.osengines.com/manuals/160fx-ring-manual.pdf