If you are adamant on keeping them both first thing you need to do is muzzle train them both - buy a couple of Baskerville/similar basket muzzles and use positive reinforcement to acclimatize them to the muzzle. There's plenty of Youtube videos on this. Once your dogs are happy to wear the muzzles for extended periods of time you are ready to contact a trainer/behaviourist for their help in understanding *why* they are fighting and producing and management and training plan to have them interacting peacefully again.
I would be interested to know if these dogs still fight when they see each other in totally neutral, never been to before, territory. Do the dogs interact positively with other dogs - both on and off-leash - both at the park and in the front yard? If the dogs are otherwise sociable and trustworthy around new dogs I can't see why they wouldn't eventually be able to interact with each-other again. Personally, I would NEVER leave them together unsupervised, nor let them be fed in the same room (including treats), nor have them share the same water bowls or favourite toys and effeminately not bones. I would also be very careful about the amount of attention they each receive when in each other's presence, as you don't want them resource guarding the humans also!
(I do NOT RECOMMEND THIS, but if you were to put the two basket muzzled dogs, on relatively long leashes together in neutral territory, would they get along then? I would have them both harnessed on long-lines that are attached to trees and the long-ish leashes attached to martingale collars and held by two, strong people. You could all relax knowing that there is absolutely no risk of injury to dog or person and can see how the dogs interact when not stressed in the home and without barriers. Know that there is absolutely no proven theory behind this random idea of mine, it's just what I'd be very tempted to do/see if they were my own dogs.)
So muzzle train first, then get a qualified behaviourist/trainer who uses purely positive techniques (aversive methods are proven to worsen aggression) and good luck.