Bought both the Hayden's from Rockauto. If my locally owned store was still in business I would have bought from them, but they're gone.
Interesting that you're not finding an application reference. I took a lot of notes from an on-line Hayden and Four Seasons catalogs. (Turns out when I called them that they are both essentially the same company). Then made little drawings and bought the ones that seemed most promising.
If my notes are correct, the Hayden catalog showed.
1968-73 340 => 2707 thermal, 17107 non-thermal, 2747 Heavy duty
1968-73 318 => 2706 thermal, 1706 non-therrmal, 2747 Heavy Duty
But IIRC what happened is that I noticed the Four Seasons catalog had a listing for 1969 340 non-thermal clutch. When I called, they told me was equivalent to Hayden 1705 (Four seasons 36949). Then got the other cross references as well which is how I decided to try the 2705. My car probably has a little less room because it has the longer '70 up style water pump with the earlier bubble top style radiator.
The thermal units have the bimetal coil. Check the shop manual on whether your application should have it or not.
The catalogs say overall hts, and distance from pulley to fans are:
2706 3.3", 1.75"
2747 3.3", 1.62" (fan is closer to pulley)
2705 3.1", 1.53" (clutch shorter and fan closer to pulley)
I think I have another page of clearer notes in the to be filed pile...:rolleyes: