I don't know how long it would take them to send it to you, but it is for sale on their site for $10.
It would be nice if they would post it for download - even if they did charge for the download.
http://store.nhra.com/product.asp?0=230&1=267&3=180
I also found this, but I'm not sure how up to date it is.
http://www.geocities.com/boosted_eine/nhrarulebook.html