driveshaft slip yoke

I'm converting my 68 valiant from a three speed to a four speed.
The four speed I have came from a 1967 barracuda, so it has the small diameter output shaft, and the slip yoke from my valiant will slip right in.

Now for the question. Along with the four speed also came the original slip yoke, and that is about three inches longer than the slip yoke from the valiant (which is about 5 inch long on the splines)

Can I just re-use the shorter drive shaft slip yoke from the valiant, or should I swap the slip yoke to the one that came with the four speed?

Thanks,

Antoon