Clark played in both and confessed Turnbull taking ill on the morning of the 1967 final wrecked their chances of beating Jock Stein's Hoops, who became the first British side to lift the European Cup the following month.
"Not having Eddie with us at Hampden was a huge body blow," said Clark, now aged 71 but still working full-time as the head of soccer coaching at the University of Notre Dame in the USA.
"I was still a student at Jordanhill College at that time, so Eddie agreed I could meet the team at Hampden on the day. I was still sitting on my own in the dressing room at 2.15pm. It was after 2.30pm before the rest of the lads arrived and I found out they were late because Eddie had taken ill at their hotel.
"Davie Shaw took over and did his best, but it wasn't the way to prepare for a final against a side as good as that Celtic one. We had drawn both league games against them that season, so knew we were capable of giving them a tough game. But losing Eddie, who was such a big influence, in the manner that we did was just too much of a burden."
Turnbull was there when the Dons made it back to the final again three years later.
Clark says he underlined his talent as a manager by outfoxing the legendary Stein to take the trophy back to Pittodrie for the first time since 1947.
The late Derek McKay's double and a Joe Harper penalty gave the Dons a 3-1 victory.
"We were huge underdogs, as you would expect. But Eddie changed our formation to ensure we totally outplayed Celtic that day. Eddie upset those two by playing Jim Hermiston up against them as a defensive midfielder. He also had Joe playing wide midfield, in a 4-3-3 formation, instead of up front. Eddie said he did that because he felt the pace of Jim Forrest up top would make it harder for the Celtic defenders. He also knew Joe was more than just a striker. He was great with both feet and Eddie was confident Joe would be able to create chances from the middle. Eddie got it spot on. He was very much a man ahead of his time when it came to tactical battles.
"We used to get stick because we played well up the park and caught opposing players offside a lot. They call that a pressing game now, but Eddie had Aberdeen doing that in the 1960s and 70s. I always say I was fortunate to play under two of the best managers the game has ever seen during my time with Aberdeen. Eddie at the start of my career and Alex Ferguson when I finished in 1980."
Clark hopes that cup win acts as an inspiration to the Dons if they end up facing Celtic in this season's final at Hampden.
"I still watch a lot of Scottish football on television, so know how well Celtic are doing at the moment. They are very powerful and, like Celtic were in 1970, are being tipped to go on and win the treble. But I have also been impressed by how well Aberdeen have done since Derek McInnes became manager. The Dons certainly look about the only side capable of even competing with Celtic at the moment. As we showed in the 1970 final, no team is totally invincible."