I had an H100 as a sprog. They're funny bikes - a decent 11BHPwhen new, though you can bet 3 or 4 of those have leaked away over the years. They're very low geared, which means they're great for the urban cut and thrust but top out in then low 50s on the open road, so upping the gearing helps a lot.
A lot of olde air-cooled CR parts are a direct swap, so it may have been a CR head that the chap was referencing.
Transfer/inlet ports can be raised about 2mm, exhaust as much as 5.
Bending the reed valve stops to 10-12mm helps, though requires some dremmel work to the barrel casting to make room for this. No one makes carbon fibre reeds for these, but there is another reed for a totally different bike (Garelli perhaps?) that is the same, and are also avalalable in CF.
No one makes spannies for them, though a few were made for the MB80 which fit, requiring only a bracket to adapt the rear mount. You'd be lucky to find one now though.