The whole heater box setup (from cabin to engine bay), or just the controls? I thought I had the whole lot somewhere, but I haven’t seen it for 15 years!
It will quite happily run on unleaded. I have a 1978 and 1980 127 with the 1050cc. The later one was modified for unleaded at great expense before I bought it. There’s no difference at all & Fiat at the time said it was ok if you avoided long periods flat out (that’s rubbish too). Experts said many cars would run for 100k on “lead memory” before needing a rebuild - that’s a long time, but anyway the 1050 was an advanced engine & doesn’t knock/pink at all on regular unleaded.
I do give them a tank of super unleaded once in a while, just as a treat, but I’m not convinced it makes any difference!