NAD27 Ellipsoid is Clarke 1866, whereas NAD 83 ellipsoid is GRS 80 which is similar to WGS84 North American Datum - Wikipedia, the free encyclopedia You will have to use a Datum shift from NAD27 to WGS84/NAD83 whereas the shift between NAD83 and WGS84 is almost negligible Reply 0...
(utm:utm-to-lat-lon 465814.3743203891d0 4346220.137838842d0 13 :ellipsoid "WGS72") 39.26465442463012d0 -105.39627074272353d0 * (utm:ellipsoid-names) ("NAD83" "WGS84" "GRS80" "WGS72" "Australian1965" "Krasovsky1940" "International1924" "Hayford1909" "Clake1880" "Clarke1866" "Airy1830" "Bessel...