Q: Is this the 'World Class' T5, and does that matter?

Yes. World Class T5s were introduced to hold up behind V8 power (as opposed to the earlier, weaker non-World-Class units built for V6 applications), and that's what you want behind a small-block swap. Like all factory World Class T5s, it uses a 10-spline input shaft.

Q: What bellhousing and flywheel does this need?

A 157-tooth bellhousing and matching 157-tooth flywheel for 289/302 applications (351W/351C use the larger 164-tooth pattern instead, not this one). Also match input shaft length to your bellhousing - Foxbody-spec T5s use a shorter input shaft than some earlier, non-Foxbody applications.

Q: Will my factory driveshaft still work after the swap?

Usually not as-is. Builders converting from a 3-speed or C4 to a T5 commonly find the driveshaft needs to be shortened (and re-balanced) or re-splined because the T5's overall length differs from what it's replacing - plan on a driveshaft shop visit as part of the swap.