Andersen awning operator

A contractor from Montpelier, Vermont says:
This operator is from an Andersen window. It looks like it's from the 60s.
-- The arms are approx 11 1/4" long
-- The track is 27" long
-- Fully extended (closed position), the arms measure 25 1/4" long, from the end of one to the end of the other (not counting the shoes)
-- The screws that remain visible inside are 3 3/4" apart
-- The screws that get covered by the trim are 2 1/6" apart

It's likely that this operator is no longer available. Do you think the Long Arm awning operator 39-389 might work as a substitute? The window is almost 4-feet wide, so there's plenty of room for the arms and track. I don't mind modifying the window trim that covers the operator if I need to. If I could make this work, am I correct in understanding that I just need to order 39-389 and crank handle and that's it?
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A contractor from Montpelier, Vermont says:
I just noticed that the Short Arm operator 39-390 has 11" arms. It seems that would be a better fit. I measured my arms all the way to the gears. It may be that they are actually 11" arms, depending on how far in one should measure.

By the way, there is no part name or number stamped anywhere on the arms or any other part of the operator.
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Bob from SWISCO responded:

Thanks for posting. I agree, the 39-390 looks like the better replacement for this old operator, though depending on the age of your old operator, some adaptation may still be required for it to work; I can't say for certain. For a new handle, see our 39-286

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