I would suggest checking out a Gear Vendors Overdrive unit. It may be out of your price range and may not, I don't know; but, everything I've seen or heard has them performing better than a 700R or 200R in cars with a bunch of horsepower.

Here's a link to their site:

http://www.gearvendors.com/hotrods.html

The best part is that since it plugs onto the back of your TH400 which may already be built for the strip, it takes the guesswork out of it. Anyway, lotso luck with your search.

Cheers,
Dutch