Ok, so I have all the gold bars, now where is the best place to sell them? No one has that much money on them. Gun Runners has 8000 caps every few days.
Thanks

Sell one bar, take the 8000 caps, make up the difference by buying expensive ammo. Then resell what you won't use when the cash gets replenished. You'll lose a little even with high barter bot it's better than selling for only the 8000.

Personally since it's so easy to make caps in this game, on the character where I got them all I have them all in my bathroom in Novac, looks pretty cool.

Before leaving the Sierra Madre you can also take them to the scattered holovendors and sell some of them for pre-war money.

Be sure and do this. They carry 2500 units of pre-war money. That's 25000, so you can basically get rid of two gold bars and get your full money's worth.
Afterwards, just go the the Gun Runners, the Great Khan Armorer, that NCR guy at the damn and the NCR dealer at 188 Trading Post. All of them carry either a lot of money, a LOT of ammo or both, so you'll be able to get your money's worth. Great Khan armorer will actually give you a perfect 1:1 buy-sell ratio if you're liked by the Great Khans, so you're free to buy ammo from her, then resell it to other 1:1 ratio venders who just don't have the money/supplies to buy the gold bars directly. I think the Followers will also give you a 1:1 ratio if you're liked by them, so you could go to the Great Khans, buy a bunch of ammo (which they ALWAYS have) in exchange for the gold, then take the ammo and sell it at the New Vegas hospital and to Julie.

Another option is, at least for me...

Mick at Mick and Ralph's never refreshes his inventory. If you always make your repairs at Mick and Ralph's, he eventually earns so much that you can sell a Gold Bar directly to him.

well what I did was sell like two to the gun runners and buy all the ammo and mods and guns I did not have and some doubles