Rusty Wallace did 228 mph at Talladega Superspeedway without a restrictor plate in 2004. The new car probably could do a bit more than that. Racing at that speed would be insane and all the safety advances since wouldn't be effective. Further, they were implemented because Bobby Allison crashed into a retaining fence at around 210 mph. This is big no-no in NASCAR because fan's shouldn't be in danger[1]. Looking at what has happened in other series to fans at high speed needs to be a consideration.
I don't think a race at 228 mph would be safer than a restrictor plate race and I am pretty sure it would kill more people.
1) look at all the attention to the Nationwide Race where the catch fence failed
smaller engines for one, maybe even make them production based. Part of that goes back to relevance to road cars. I test drove a Fusion when I was car shopping. needless to say a pushrod V8 was not one of the options.
I don't think a race at 228 mph would be safer than a restrictor plate race and I am pretty sure it would kill more people.
1) look at all the attention to the Nationwide Race where the catch fence failed