Ryan is one of my favorites. I assembled a run of 1969-80 recently, using cards I had and new cards too. Some random thoughts on the issues' relative difficulties:
1969: Semi high number and a great looking 2nd year card of an Amazin' Met from the miracle year.
1970: High number with tough color borders
1971: Black bordered nightmare in higher grades
1972: semi high number, first Angels card
1973: tough to find centered and sharp. I think 1973 has the worst card stock of the decade.
1975: centering and color borders
1977, 1979: usually o/c
1974-1976-1978 are no more difficult than any cards of their respective years.