OK, I need to clarify my previous post. The 60-65 3 speeds had a 4 bolt side cover and the 3 speeds were all the same. In 66 only the OD trans was a Saganaw with the 7 bolt side cover, the regular 3 speed had the 4 bolt side cover. The shift rods on your 64 were correct for the original trans but will have to be modified to fit the Saganaw which has different shift levers and different spacing on the side cover. The likelyhood you are going to find the 66 3 speed OD shift rods are slim to none as not many of them were built. 67-69 was a different truck so I am not sure those rods would fit. I put a 3 sp (non OD) Saganaw trans in a 65 a while back and we had to do some major bending to the rods to make them work.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine