Sadly there is really one company actively building new chassis and that’s Tim lynch, he builds the diamond chassis as well as the Lynk chassis that kkm uses in USAC midget competition. Most of the cars are using 636 Kawasaki engines or there a few Suzukis out there. Acro engineering makes the rearends and many of the other parts and are located in greensburg. Randy literal usually has or knows of some nicer up to date cars for sale. I don’t do facebook but I believe there are a few groups with parts/cars for sale. Lots of those older cars haven’t been updated and still have the old Honda engines that they used for ages. DRC built some chassis a few years ago too. There are a lot of older Beast chassis floating around as well.