Crettz
Alfaguys junior is a late model 4 headlamp flush fronted car. The GTA was what is known as a 'Stepfront' these have a slight step in front of the bonnet (hood).
The step front Cars were the original design they always had two headlamps, they were superceded by the smooth fronted cars in 68. My 1750GTV which you can see in my Avatar is the 4 headlamp smooth front type.
To complicate matters they carried on building Juniors including GTA juniors with stepfronts during the same period of time as the GTV's like mine. Eventually the Juniors (1300 and 1600 CC cars) had a smooth front 2 headlamp design, laterstill a four headlamp design with a differant grill, extarnally these late juniors were almost identical to a 2000GTV.
The rest of the body was practically identical all the time, though around about 1968, the rear wheel arches became slightly higher.
These developments were spread out of the period of 1964 right through to 1976 or so.
It's all a bit complicated!
An original GTA by the way (1.6 or 1.3), although apparently similar actually has a lightweight body with many aluminum panals, these Cars are very rare and very expensive, 60.000 to 70.000 euro's or more.
the even rarer GTAm, the four headlamp ones like the one in your link are virtually priceless, only 10 were made (I think)