Geographic Transformation for Atlantic Canada

Hi All,

I am trying to convert contour data from NAD_1983_CSRS_UTM_Zone_20N to ATS 1977 MTM Nova Scotia Zone 5. Our CAD and Civil 3D folks work in this projection.

When I try to project it, the anything but "Optional" Geographic Transformation does not appear to have an option that works.

HELP!!

Thanks in advance for any input you can offer. Please don't suggest I go to the help, because I've been all over it for the last 2 hours.

Andree