I think the cup & busch cars have to have a passenger window at tracks over a mile. I remember Brett Bodine's falling out at Atlanta I think? Was a few weeks ago though.
Widow also mentioned that the Busch cars use a smaller carb. I'm pretty sure the cup car's carb is 840 cfm.
The ASA series is in the second year of using the same engines for all their makes. The Chevy Vortec V-8 which is fuel injected.
Not sure if the entire rule book is at their web site but you can view all the rule changes for 2002 in great detail at their web site. http://www.asaracing.com/tech_truck/tech_truck.html
ASA opens their season tomorrow at USA Int'l Spdwy in Lakeland, FL.
Don't know much about ASCAR.