The clutch has more splines than the input shaft? While I was reading this I was thinking the exact opposite. The SVO clutch disk should have a 10 spline hub.
I'm wondering if someone didn't swap transmissions in the SVO before you owned it. Maybe threw in a RAD or SROD when the original T-5 failed.
You've sat both transmissions side-by-side and compared them right? Are they identical? They should be.
To get that
trans to work, you're going to need a bellhousing for a T-5 since it doesn't sound like you have one. You'll also need to get the right clutch, or at the very least, a clutch disk with the same diameter as your current pressure plate with the right hub for the T-5.