I decided to retro fit the existing fixtures with 8 foot led frosted tube lights. I'm happy with the results. With the diffuser in place it's a nice even light.
If you want additional information on this google LED Type B tube conversion. Type B are the ballast bypass which run on 120 volts bypassing the ballast. I am not sure which tombstones or specific lamps the Diamond lights have (HO are single pin- standard are bipin) but in any case Leviton (mfg of tombstones) did a white paper recommended to use newer tombstones as many older ones are not designed for line voltage. Just make sure the newer tombstones match the LED tubes.