Transmission yokes?

I recently swapped my girlfriend's 3.03 3-spd out of her 1967 Mustang and put in a T5 out of a four cylinder Mustang. Car's like a whole different animal now! Surprisingly, I was able to use the stock driveshaft and stock transmission yoke. However, the T5 is leaking a small bit out of the tailshaft seal. I didn't change the seal because it's nice and clean and flexible still. However, I'm wondering if this might be leaking because the yoke's slip joint OD is slightly smaller than a T5 yoke? Does anyone have a way of confirming this? I don't have a T5 yoke on hand or I'd check it myself.

My girlfriend is aware she may have to solve this leak issue by buying a new yoke (and she needs a new one anyway - I put the new u-joint's cups in by hand!), so my next question would be, does anyone know of a solution where we can replace this yoke with a new one without having to have a new end put on the driveshaft? The old lady's budget is just about used up for this project, and I'm not sure but I would think a T5 yoke uses a larger u-joint than the stock Mustang M/T driveshaft's u-joints - which look like something more suitable for a steering column.

Thanks for any help, guys.

I'm interested in this out come also, I have a slow leak from the same spot, making my exhaust pipes all dirty and burnt. I tried the seal myself and it still leaks (I even had the shop install a new one for like $40 and they have been replacing it every 6 months because of thier lifetime warranty ) even after 3 replacement seals

My next step is to just replace the C4 Yoke with a brand new T5 Yoke, then have the shop replace the seal one last time.

I'll keep you updated when/if i get the funds to do it.

Some years ago I changed my F100 from the 3.03 to a T5 and I just used the same yoke and never had a leak, but I did use a new seal in the T5.

Fred