You do not need the long intake manifold to mount the Sha 15/15 Dellorto, on this red A model 50V, I used the big 15mm shorty. This ped will do 35mph. It will fit right on the shorty intake made for the 12 mm Gurtner carb. The advantage is that it will not hit the bottom of the fuel tank when the engine is in the up position at full throttle. Also, there is no need to customize the throttle assembly; the slide will go all the way up and down with the stock grip. This is true for the 77/78/79 50L/50V models.
You can also use the shorty from a 10mm Gurtner carb setup to install the 15/15 Sha Dellorto. On a B(25mph) Model 50V, you have to use the insert that comes off the 10mm Gurtner carburetor so the Dellorto will fit right on the 10mm shorty. The Dellorto will make the moped go just over 30mph.
Here is a shorty for that fits the Dellorto 15/15 Sha for a Motobecane