Dellortos are good too. I'm the same way, I like mopeds 100% original.
I had a 72 Moby-X and it was next to impossible to find a decent Gurtner for it that would fit properly due to the small engine configuration as well as limited space for the carb. I purchased 3 or 4 of these and after finally getting the right one, I cleaned it up and put it on. In 2 weeks, the Gurtner was already gummed up- even if I had an inline lawnmower filter.
That drove me nuts. I love to work on mopeds, and the such. But when it comes down to cleaning the same carb over and over, it can get old fast.
Gurtner also needs to be airtight in order for it to work properly. Other carbs can deal with a little bit of an air leak. But not Gurtners.
Best of luck on your project.