Brief overview of T5 in a II based on many discussions/postings.
T5 bell fits with OE iron manifolds only (no tubular headers)
T5 bearing retainer OD is larger than the IIs, so if a II bell is used, retainer or bell will need to be modified.
T5 input shaft shorter than II
T5 mount located rearward of the II mount position. Many have said just use longer (~7-8 inch) bolts to space xmem back, but I plan to look into modifying "toilet seat" to move mount ears back on the rail ends. Long bolts seem a little shaky to me.
Shifter located approx 2" forward of the II shift tower. Deeper II bell helps this somewhat, but requires pilot bearing spacer to make up for shorter input. Believe '94 and '95 T5 have slightly (~.75") longer input.
Interestingly, the '94-95 3.8 T5 is rated at the same Torque capacity as the pre '90 5.0 T5. HOPEFULLY a 3.8 T5 should be somewhat cheaper than the 5.0 version. Should be plenty if OD is the goal.
All in all, if you're just looking for the Overdrive, I'd use the T5 bell, but if headers are planned, the II bell makes more sense, though they can be a little tough to find and somewhat pricey depending on who it's sourced from. Likewise, I'd hate to cut on a II part that's in relatively short supply.
Wish I could provide more definite answers, but my $200 '95 3.8 T5 has yet to be delivered.