There is always the South West Street Rod Nationals here in OKC at the first of April. Although it is 48 and older. I'm sure there are few other decent sized shows, but I'm just too lazy to look right now. I will post up later.
Instead of me going through a bunch of shows and naming a few, I will let you look through them. There are quite a few good shows and cruise-ins. Here are a few websites that I use to look for shows on the weekends. Enjoy.