I would change it out with the heavier one. One thing to keep in mind is the
part you installed might have stated that it was for that vehicle, but you
dont know if it met OEM specs. Most parts do these days, but that sounds
like too much play in the bearing. If that driveshaft can wobble around in
the carrier rather than the U-joints doing their job, then that is whats
goin to happen. And that will cause your vibration.

Also did you install the u-joints correctly? Are they greasable u-joints and
if so, have you greased them? When you installed the U-joints did you put
the grease zerk in between the driving yoke and the driven yoke pointing in
the direction of rotation while in drive? If you didnt, then you need to
pull them out, inspect them thoroughly and re-install correctly. As an
example,  on a single drive shaft, I would install the u-joint with the
grease zerk in front of the yoke on the trans and behind the yoke on the
driveshaft (for a driveshaft that turns CW while in drive). That way when
the vehicle is loaded there is compression on the zerk area, and not
tension. If they arent installed correctly, the weaker part of the web where
the hole for the zerk is drilled can allow the u-joint to stretch slightly
when under load, or rip completely apart. That can cause your vibration.

Lastly, did you grease the slip joint between the driveshafts when you
re-installed it, and did you clean it as well?

Ford Tech

Yes. It's always worth the money to try parts that actually fit.