It is my understanding that Bronco's went with a Spicer yoke in 1970. Is a Spicer yoke required for install? or will the older yokes work just as well?

Our drive shafts do require the use of the Spicer style yoke. They are not interchangeable. If your yokes bolt mount holes measure 1 1/2 x 2 5/16, that is the Spicer yoke. If the hole c-c is 1 7/8 x 2 5/16, that is the Borg Warner, and the t-case yoke(s) will need to be replaced. Always best to measure what you have in front of you.