I am guessing you are right about the make over. It does look like a quality job except for the "total lose lighting". The charging system was likely shot also. The 3 1/2s used magnito ignition so they really do not need a battery.
As for the ride, I have a really low milage 1976 3 1/2 Strada, and owned and ridden dozens of bikes, and I can tell you that there are few bikes on the planet that are any more fun to ride. Yeah they won't set any speed records but they move pretty well for a 350cc bike, handle even better, have six speeds, are way better on the highway than my cb350, you will be the only kid on the block with one and you will not meet anyone who has or had one that won't tell you the same. But yes they do have problems, what doesn't. You have to keep a close eye on the timing belt (which, by the way is a standard toothed industrial belt you can get anywhere, Grainger, McMaster-Carr etc.) and you do have to kick them... ON THE LEFT SIDE! I will bring it to the track (NHIS) in May and you can decide for yourself!
Ride and Race Safe!