I have been following NASCAR for over 40 years and have attended the Daytona 500 for 38 consecutive years......To answer a few of your questions. NASCAR changed the size of the restrictor plate Saturday morning by 1/64 of an inch. That reduced the horse power by about 12 to 15 HP's. This in turn slowed the cars about 10 MPH. NASCAR does not want the cars running over 200 MPH for fear that they will become airborne and fly into the stands. I was at Talladega when Bobby Allison almost did just that. It took them over 4 hours to repair the catch fence and one fan went to the hospital with non-life threatening injuries. It was a REAL MESS.
With Talladega just being repaved it was smooth and VERY FAST. Speeds were near 200 MPH during practice, so NASCAR decided to put a smaller restrictor plate on before qualifying. The size of the restrictor plate has been the same for about 3 or 4 years now and will probably go back to the larger size when they return to Daytona in February.
As for the engines each mfg has it's own version of a block. They do not use stock blocks anymore. NASCAR has even stepped in and is making them all use the same bore & stroke in an effort to reduce costs. Dodge was experimenting with bore & stroke for different size tracks and NASCAR got wise. They are allowed to run 358 CU. IN. with 12.5 to 1 compression ratio.
The hardest thing Toyota had to adapt to was using a carburetor. They will be using the same engine in Nextel Cup that they have been using in the Truck Series.....Hope I answered your questions.
BTW......I am a FORCE Fan as well. Used to go to the GATOR NATIONALS every year. Loved his LONG burnouts!