I believe that the FIAT Palio is the source - it had a 1300cc engine with 8 valves and multi-point injection producing 72 bhp. With a different cam profile the 78 bhp of the GTie would fit in perfectly. If not the Palio then perhaps it was based upon the Thema 8.32 engine ;-)
The Delta used two different "1300" engines but neither of them are Fire engines. The later version was of 1301 cc but different bore and stroke from the Y10/Palio engine.
The source's is the 1.050cc engine fitted in the 127, and then developed in the 127 1.3 Sport (or Abarth)...this engine has been a little revolution in the Fiat production because of the Sohc structure and timing belt's presence instead of the chain!
OK - The 127 1300 Sport block has the same bore and stroke so that must be the same block. The Fiat 147 was the Brazilian 127 and it used the 1301 cc block but I have not yet found a definite confirmation on that and the new head assembly that was in the Y10.
If you need those infos I can try a research among the passionates' forums...the 1.050cc unit has been fitted in the Autobianchi A112, and then the turbocharged version took place in the Y10 Turbo engine bay!For years it's been the lowest displacement turbo engine...but now the MCC Smart[^]!!
The Suprex engine has been declined in different power levels...for example on the Smart Crossblade it develops about 80Hp...nothing bad for a fly-weight engine!