You might check with the folks at Texas Wildlife Supply. I have used a lot of timed bulk feeders and found them to be the best built for maintenance and longevity.
Reason I'm suggesting you call them is they make interchangeable heads so their bulk style feeders can be free choice, spin cast, or timed bulk simply by changing the heads out with four bolts.
It's been a while since I've been to their plant in Brady but the last time I was there they had some trade in units sitting in their yard. They refurbished them and then a person could buy whatever head they preferred for what type feeder style they wanted.
I purchased quite a few of those and put different heads on them as I desired . The ranch is still using them to this day.
I don't know if they still do those or not but it was a bargain back then.
I have a few of them up here when we moved. I'll try to go get a pic and post it so you can see what I'm talking about.
TAMU Wildlife & Fisheries Sciences