I'm not a II owner put came across some info in the course of gathering parts for a T5 swap into my 66.Some time ago, I ran across someone's II site in which they were putting a T5 in place of the 4 sped on their 302. As I recall, the overall length of the T5 was shorter then the 4 speed and the handle was too far foward. I think the difference was something like 5/8" or 3/4" For my 66, I'm using a '97 V6 T5. As you know or maybe you don't, the 94 & up T5 is 5/8" longer then the 85 to 93 V8 T5's. I think using a 94 & up V6 or V8 T5 with bellhousing would make things work out easier.
Don't worry about the V6 T5 strength, it's the same unit as a V8 rated @ 300 ftlb. I've personally have spokenwith D&D, Hanlon & Tremec and all 3 say the same. In fact, Tremec unloaded a huge number of "V6" T5 to these guys who have just swapped out inputshafts and turn around to sell them!