I have an '01 dually with the factory hitch setup on it. I am curious, what size pin did this take in the receiver originally? The hole on mine is egg shaped and larger than the 5/8" pin I normally use. 

 I can take some pics if needed. I am probably going to have to buy a new shank already since this truck sits much higher than the suburban I used to pull the camper with. I'm hoping I don't need to replace the hitch right away as well.

 We don't usually go far with the camper maybe one or two trips a year no more than maybe 60 miles round trip. Eventually we will venture further but for now I just need to make it safe.

It should be 5/8". 

 

I had to replace the OE hitch on my 05 as both the 2x2 opening and the 5/8" pin hole were wallered.