George,
Firebase 29 was located on Hill 824. It was never abandoned that I know of. One of my first missions was a LRRP extraction near this base in March of 1968. The NVA tried to over run it in May of 1968 just about the same time Operation Matthews had begun. It was also had the perimeter breached in Oct. 1968. I remember going in there and hauling wounded and dead out.

We were doing FOB II during August and September of 1968. Because of that we were somewhat out of the loop as far as the 4th Infantry was concerned. But I do believe that Firebase 19 was on Hill 1258. This was south of Firebase 29 in the Plei-Trap Valley. That base was abandoned and retaken a few times during my tour as many of the bases in the Plei-Trap were.

Wish I could be of more help. Let me see if I can find a grid for Hill 1258.