I'll look for a very small tube with vanes on the outside to cut little pieces off. Converting my base Carrera 904 GTS to 904-6 spec sounds fun with the twin megaphones. I'll have a look, but a few projects are already on my build table.
A little note, the 904 was originally designed for the 6 cylinder engine, but at the time development in power was still in the beginning with the 911 2.0 engine and Porsche's Carrera 2 GT 4-cam engine was more powerful. Eventually at the end of life of the 904, around 1967, Porsche developed the 901/20 engine with twin spark plugs, 46 weber carbs and 220hp at 8,000rpm. This engine made it into the 904-6 (I think six factory fitted 904-6 cars were made) and eventually the 901/20 was used for the 911R. 904 Customers retro fitted many of the 6 cyl engines into their 904s too.
I totally forgot, here are photos I took in 1989 of a factory '67 911R 901/20 engine with mechanical fuel injection.

