I can't figure out what kind of bottom bracket i need. The shell threading seems to be English (right-side cup is reverse-threaded), but the width is 70mm. English brackets only come in 68 and 73mm? The inner diameter is 34.6mm
Not true. Bottom brackets on most recreational bikes are 68mm or 73mm. But almost all bikes that were made for ROAD riding in the older days were 70mm wide. So you have measured correctly. Be careful, though. Italian threading is different than what we now call Japanese International Standard (JIS). And French can be different again. Your old axle should have a number and a letter stamped onto it. The number should be 5 designating a 70mm wide BBshell and then the letter designates the specific style of your axle. With those bits of info you should be able to purchase another BB. I recommend visiting a good quality bike store for more info about this stuff and they can tell you whether you need a special BB or just a standard 70mm one. And watch out too if your cranks say either Maxi or Stronglite. Both of those cranks had different taper angles than standard BB axles and will require a special axle again. YIPES! good luck
