Nascar limits the size of the overhead valve engine to 360 CI. What they do to the insides of the engine is solely up to the team. There are certain precious metals banned, but as long as the size of the engine isn't altered, it is a free for all in that respect. Not really that far of a stretch from the weight limit debate.

On a side note.. Seeing some old geezer in a skinsuit was the last thing I expected to see in this thread.