Input V is about 340VDC currently. It's more of a prototype for something in the 650V range and maybe larger at a point(?) so I even if I ditch the hollow state later and go transistorized it shouldn't cost me much. Here is a schematic I based it on, it's from an HP-400 Oscilloscope. It's actually to mess around with other vacuum tube stuff.
I don't see transistorizing this being too difficult really, I'm likely going to get some 130V Zeners to ditch the 0D3 with as well. Overall the circuit seems to work well, I haven't load tested it yet but it certainly swings voltage about 80-90V with the stockish resistor combination. I'm hitting a hamfest this weekend so the oddball variants of these (21V Filament) may be on the list since they're only a few bucks each.