A quick look on one site shows a YD as a 67 OR a 69:
HP= 290
Cubic Inches= 400
Trans= A
Code= YD
Compression= 10.5
Cam= 254
Heads= 143061 (#46 HEADS IN 69)
Carb= 2
Year= 67 or 69

With that date code I would assume it was built for the 69 model year?

If I get a chance I'll check some more info, or maybe some one will add more... - Brett!