NHRA is the National Hot Rod Association, and the IHRA is the International Hot Rod Association. The difference is kind of like the Nascar series...You have Busch Cup, which is the smaller series less popular category, and the Nextel Cup. the Big Dogs...Really popular. On the flipside, you have NHRA which is like the Nextel Cup where the cream of the crop run, and then you have the IHRA which is the lesser popular, smaller scale, but they run in Canada, whereas the NHRA is USA only. You see crossover drivers in the IHRA just like Nextel/Busch...Hope that helps.
NASCAR (all caps...) is divided into divisions with Busch being the 2nd tier league (ala English 1st Division compared to Premier League). IHRA and NHRA are competitors, like ChampCar and IRL. They do have their crossovers, but not as many as NASCAR.
And try not to talk to harshly about the Hemi Dodge to FP and Jim. The season's not been going well. This week was pretty awful.
Scotty was cool and an IHRA God - but he just couldn't cut it in Top Fuel. He tried to quit a year earlier than he actually did and Jim convinced him to stay another year....he had his own ideas about how to run a Top Fuel team and unfortunately, they didn't work out... Combine that with the last year he was in NHRA Scelzi came on board and started kicking ass - Scotty went back to his roots and now his kid is kicking ass as well...Scotty is an awesome guy and a great competitor - he just wasn't quite ready for NHRA yet.....maybe someday....
The deal with Scotty going back to the IHRA is that he wanted to own his own team again. When he first started in the NHRA in 1999, he ran his own team and did things the way he wanted. When they teamed up with Don Schumacher Racing in 2001, he felt that he did not have control of his team or his car. Scotty loves being a team owner and that what he is. His son drives his old car in the IHRA these days. Hopefully that clears some things up.