Re: old pressure tank to newer tank conversion????
Lots of folks have done that conversion. The site you linked to shows a good way to do it on that model. Other models will require different techniques.
However, the dangers listed on that site are way exaggerated. Since rebuild kits for the two-line pressure tanks and o-ring seals are available for the connector fitting, there are thousands and thousands of vintage Johnsons and Evinrudes operating happily and safely with the old system.
So, I take it that you have one of these vintage outboards and tanks. How are they working? If they're working well, the tank is holding pressure, and the priming pump is working, just check your hoses for cracking (new ones are available). If your connector isn't leaking, then don't worry about it. You can replace the o-rings in it, though, if it's leaking or just for the heck of it.
If the tank is leaking air, you can buy a rebuild kit, or...you can do as that site suggests and switch. Note that it is not "Mukumi" as the writer on that site said. It's "Mikuni." There are other pulse operated fuel pumps also available that will work just as well, too. Depending on your outboard, there may be even an easier way to go, using an OMC pump.
But...if your system is working fine now, it will probably continue to work fine into the future. Heck, I have an old two-line tank that is well over 50 years old, has never been rebuilt, and is still in perfect condition. I'd use it in a minute, but I don't have a vintage OMC outboard any longer. I keep the tank because I'm sure I will have one at some point, and the tanks are expensive to buy.