The chassis codes are used sparingly for GM and Ford's North American cars, with most being referred to as letter-body (GM) or insert-big-cat-name-platform. Those aren't of too much use, as they usually don't indicate generations too precisely.

But, if you dig deeper, you can discover GM and Ford have another tier of chassis/development/production codes which identify vehicles better. Feeding one of those into Google usually reveals "technical" articles with many of those mentioned.

Example: http://findarticles.com/p/articles/mi_m0KJI/is_12_113/ai_81147809/pg_2

Thus, for example, the DEW98 Ford Thunderbird (the most recent, retro-inspired generation) is [M205], and the Saturn L-Series is [GM2902] (a platform shared with the Saab 9-5).

I will post more examples in due course, and invite you to join in (and admins to apply ).