Jim,
Some Fiats, eg 600 were assembled in Australia in 50/60's to avoid the prohibitive import duty that was levied on fully imported cars to protect a developing domestic car manufacturing industry. The extent of local content in these "assembled" Fiats (and a range of other makes) is unknown, but was probably restricted to a relatively small proportion of total vehicle content. There was no VAT at the time, but there was a considerable level of retail sales tax on all motor vehicles, locally manufactured/assembled or not. VAT was implemented but a few years ago, along with a phase out of previous sales taxes. Tariffs on imported vehicles have been phasing out over a number of years now, and are now minimal. I am unaware of any "kits" being available at the time for individuals to acquire.
Attached are photos of an Australian market right hand drive Fiat 600 engine bay, stamped chassis number, and the assembler ID plate from Pressed Metal Corporation Sydney, similar to that attached to most 600's available here. The Australian assembler ID plate states local stock number and chassis number identical to stamped firewall chassis number. The cars also had the standard Fiat rectangular plate with spares/chassis /motor numbers but that is missing from this vehicle.
Trevor