Rob, since your tray is in good shape, if you're using a more or less standard sze battery, just get the OE hold down & bolt/screw - available from AA, Pelican, PP/Automotion, etc., - but do use a battery anti-acid pad & a sealed battery at the least, if not an Optima coil/gel cell or Odessy dry cell - for which the same sources & others alos sell adapter brackets for Optima & Odessy.
Should be no need to create some custom bracket, unless that's what you like to do for the Halibut!
PS _ the problem with 914 batteries wasn't tipping, but acid leaking from the old open cell &/or fumes with acid from those & closed cells re-hydrolyzing on & eating through the cloth covered fuel lines when rain water, etc. washed into the engine bay.