I have a very old coach with a stock carburetor. It has been no problem. The rest of the fuel system has had to be replaced because it fell victim to poison gasoline. If anything is older than about 2000MY, it may not be compatible with 10% alcohol that is in most motor fuel these days. But, to fix it all you have to do is replace all the rubber and corroded steel (if any) in the entire fuel system. And, get ready for vapor lock problems. Cr*pahol fuels get a special wavier so they can pollute more with higher vapor pressure.
In fact, just getting EFI may not help. It just means that the leaking fuel line will spray fuel farther because of the higher pressure.
EFI is better at high altitudes, so if that is an issue, that may be the driver you need to look at long with the rest.
Good Luck
Matt