It's funny, I actually considered using those from my 4x4 days...I ended up using a cast eye bolt from ACE Hardware, 3500# rating, 1/2" diameter shank and about 1" hole. Not too heavy and just drilled holes on the underside of the bumper for instalation. You may want to search for some that have a 2" center opening. If I had the money, there are some nice ones on the various racing products sites.
When trailering the car I like to be able to pull down and out or down and criss cross with the tie down straps to keep the car from moving on the trailer.