Best Practives for Landing Page Testing

I am interested in deploying a concurrent landing page test for one of my major paid search clients. Essentially, they have three distinct landing pages that they would like to test. I would like to be able to concurrently test the landing pages in order to eliminate any time-based confounding variables.

I have thought that the best way to do this would be to send users from the engines to a page which, based on some sort of random script, serves up one of three landing pages to test. Has anyone here utilized a similar method? If so, what was your experience? Also, any resources on how to implement such a test? How did you handle tracking?

Please note that because we track at a keyword level, using Adwords to rotate different landing pages is not a possibility (unless the entire campaign is reorganized w/ one keyword per adgroup).

Any suggestions?

This seems like your solution. I wouldn't use a redirect script of anykind since Google will not like that.

AdWords will allow you to create a more stable testing environment because you can control the positioning. Create 3 adgroups each with 5 keywords or so (same keywords in each one) with each one going to a different landing page and just run each for about 3 days. Just make sure you run them on the same days.

Yes it's longer but this way you'll get the best data IMO. I do it all the time and it's worth knowing what works and what doesnt before devoting any development time to any project.