The next thing I would do is find or decide which club or association I'd race with. You would probably prefer the closest but I'd try to go with an ARMA or USLMRA affiliated club. Next I would decide what class I want to run. If you have no previous racing experience then I would start with a Super Stock. They are fun, probably the most competitive, and cheapest to build. Plus you get seat time and you could always step up to a faster class after you get some driving experience in the hot seat.
Sorry had no idea this was posted in drag mowers. I have no clue about these, thought it was circle track. Again sorry not trying to mislead you just omit what I said up there.