casement window operator for Norco

My picture is listed on the left of a Norco casement window operator crank out

assembly. Numbers on the operator; R30842 and on the arm 20755. The long arm is

9-1/8" the short arm is 3-3/4".

Are the numbers I selected correct or not; 39-155 and 39-156?

I need a right and a left one, I have handle and covers for both.

Please guide me in the right direction.

I measured from the end of the arm instead of to the center

of the assembly hole, That measures 10-3/4". So it looks to

me the 39-155 and 39-156 should work. But you know best so please advise.

Also, the one operator assembly has no crank out driver, how to I get that window open to take it out????

Thank you.

Don