I believe the eye nut is the Chicago Hardware Drop Forged Eye Nut C-187A--- that's what mine were on my 2001 Hawk.
According to
their chart, the tap size is 3/8-16.
The bolt is an 'elevator bolt'. I took a look at one I took off my Hawk and its overall length is 1-1/2" and it has a plain cap (meaning no grade markings)
This Amazon listing appears to show elevator bolts that would fit. Of course bolt strength would be a concern and the listing says they are Grade 5. Oddly (to me, anyway), it says the Manufacturer Grade is 2.
You may also want to check the wood closely on both sides of where the elevator bolt goes through. On my camper, an elevator bolt had pulled through the wood a bit so I ditched all the elevator bolts and added a plate above (to spread the load) and used regular hex-cap Grade 5 or 8 bolts. That does mean I have a bolt head and plate sticking up where an elevator bolt was fairly level with the wood surface but that doesn't matter to me.
I also replaced the eye nuts with eye nuts with a wider base (I bought them at Fastenal) My theory is the tapered base of the C187A eye nut allows the eye nut to tilt a bit under heavy load (if the load isn't a straight-out pull) and that stresses the bolt in an unexpected direction.
Another approach is to upgrade the tie-downs to the
three-bolt style ones shown in this post. That's probably a classier and stronger solution overall but is more expensive and may present some retro-fitting problems.
