Having driven several Kielser equipped cars and a couple Passon trans cars, here's my .02.

1. For a true "no hack" install the nod CLEARLY goes to Passon
2. If you drag race you'll like the Passon, the Kielser is not a fast shifting trans, a bit too sluggish and notchy, especially at higher RPMs
3. If you want the strongest trans, Passons will take more HP than a Kielser by a fair margin
4. For cost and ease of install, Passon wins
5. For the best highway crusing O/D situation, Keisler wins due to it's better high gear ratio
6. Fuel milage Kielser also wins, same reason
7. Service - Passon hands down
8. With a 3:54 geared car that you do not want to modify beyond clean/simple easily reversable bolt ons and is mainly street driven and occasionally drag raced - Passon
9. For a modified car that is mainly used for local car shows, street cruising, taken on a good many long highway runs and not much else - Kielser
10. If considering these two companies you should also look into Gear Vendors and Classic 5 Speed before buying, may as well see what everyone is selling before you pull the trigger. I have also driven Gear vendor equipped cars, they should be a consideration for sure, they make a good product.