Oh I don't believe the First Indiana's guns were Parrotts, but the only contemporaneous reference to them by any name is Lt. Thompson's calling them "Parrotts". I'll have to spool up the microfilm to answer your question about Pine Bluff's artillery in Jan. 1865 (sorry, didn't get the chance today), but I THINK there were no Mountain Howitzers, at all. I did look at the Helena Post Returns today, of which only a single one, dated 20 Jan. 1863, was preserved, and on that date much/all of the cavalry (and specifically the First Indiana) was away on a major expedition. Very disappointing!
Might the 5th Kansas have gotten the six mountain howitzers of Stange's Battery? That makes sense, but I'd like it better if someone explicitly mentioned the fact, historically. Gen. Steele mentions the First Indiana's guns explicitly during his narration of forces advancing on Little Rock; presumably if the Fifth Kansas already had artillery by the summer of '63, Steele would have mentioned the fact. By the spring of '64 Stange's Battery seems to be rid of Mountain Howitzers; if they passed them along to the Fifth Kansas Cavalry that would explain where they went.