Eric (SD40-2):
Here's a link to some info on the Reading HTh hoppers. Scroll down about halfway on the page. Looks like they were built in 1916-1917 and had outside ribs, straight bottom sills (not fishbelly) and inside length of nearly 33'.
Based on the photos, at least one may still exist at the RR Museum of PA in Strasburg.
And here's some info on the HTj hoppers. Scroll down to find this class. Looks like they were built in 1919 of a USRA design and also had outside ribs and a straight bottom sill, but had a shorter inside length of 30.5'.
BTW, did the cars arrive safe and sound?