Another way to look at using the electronic speedo T5, is that we know the little X-box is pricey, but possibly a money-saver in the long run. With the electronic T5's, you're getting a W/C transmission that's years newer with possibly less mileage, and the new "X-boxes" allow you to calibrate your speedo through the box. No more getting it "almost" on the money by swapping out little gears under the vehicle.
Last time I checked, they weren't giving away T5 rebuilds on worn out earlier transmissions with high mileage, and being able to have a properly calibrated speedo might just save you from a speeding ticket. When you stack these up against the price of a conversion box, and consider the ease of making speed calibration adjustments at the box, it may not be such a bad deal.
I wouldn't dismiss a good W/C electronic T5 just so I could avoid adding the conversion box.
Dave