I'll second the Metz 60CT series. My CT2 has GN 100 at 180. Your GN must presume some defined sort of reflector. I also have a Braun Hobble EF300 circa 1966 that has the same sort of kick.
If you want the head to stay the same, the pack Braun flashes put out about 500V full power, 380 half power, and do all triggering in the head. The metz packs genrate the same sort of voltage, but have a third lead that goes back to the pack to quench the discharge on auto mode, to prolong use on a single battery charge.
My braun was written off due to no 4V wet cell batteries being availbale any more. I house 2V spiral AGM 2V cells in a supplimentary housing under the battery pack to generate the 8V it needs. I tested it on a 6V UPS battery to verify the ocsilator and capacitors before sinking money into new batteries. There is a fuill thread on the rehab. Search Braun Hobby EF300 here.