From the Kodak Master Darkroom Dataguides 1972 & 1970 printings(posted 8544 days ago)1972 For Tri-X sheets with intermittent agitation at 1 minute intervals, large tanks, 68 degrees F: 11 minutes; For continuous agitation (trays), same temperature, 9 minutes.
1970 For Tri-X sheets with intermittent agitation at 1 minute intervals, large tanks, 68 degrees F: 9-1/2 minutes; For continuous agitation, same temp., 7-3/4 minutes.
Both datguides say to develop D-76 at 1:1 for the same time as Microdol-X straight up (undiluted), regardless of film.
Kodak's recommendations err on the side of overdevelopment, and through out the 70's, if I remember right, they just kept on increasing their recomended development times. I'd start off with the shorter of the two times suggested (1970 times).