Stock tow hitch installation and Tomken gas skid

Does anyone know what size bolts/nuts the stock XJ hitch on a 99 takes? Do you have to remove the rear bumper to install it? I have the nut strip for it.

On the same note, I have a Tomken gas tank skid I want to put over it but unlike the stock gas skid, it does not mount with the same bolts as the tow hitch. Has anyone done the same combination on theirs?

Thanks in advance.

I don't know it off hand but if you have a subsription to peterson's 4 wheel and off-road in the more recent issue with the blue s10 on the front (I think but don't quote me its the nov. 04 issue) they have xj mods towards the back and they have a skid row gas tank skid and they give you the bolt dimensions. Hope that helped if not i'll get back on and post the dimensions.