I mounted four flat eyelets in my floorboards (two on each side) and then use a ratcheting tie down to hold my board to the tunnel:
It's not the fastest in and out but the price is right and it gets the job done. I don't like how some of the racks out there make your board hang way off the end of the sled, it makes it awkward if you need to pick up the rear end.
The holes I used are in the footboards. On that note, if you do drill in those be careful to look underneath first, some sleds run the coolant lines under there. Pip drilled in to his when building his rack, but plugged the leak with a sheetmetal screw and was good to go. Having a beat ass sled that's 11 years old makes it easier to drill holes