The shocks would replace the 'suspension max extension position stop' that the straps do.
I think the straps have another function to do with body roll, etc. but not exactly sure ... maybe somebody else knows more.
Moving on to the rear suspension setup of the GTA and GTAm's, I have seen the sliding block arrangement a very long time ago. BUT what do they do to replace the A arm on top.
Sniady has replaced the A arm with a rose jointed trailing arm ... does this allow full suspension movement without blinding?. I assume it does because it looks like you still have rubber bushes in the lower trailing arms ... and thus flex is still possible. The panhard rod would lower the rear roll centre to the centre of the diff according to all the books, but that is an improvement from the top of the diff.
I am real interested to know if the GTA/GTAm's used a 4 link trailing arm system or what?
Many years ago I built a club car that had to use a beam axle for the rear. I have always admired the Alfa rear location but the disadvantage is the very high roll centre. Thus I flipped this concept upside down and had a lower A-arm (and thus very low rear roll centre) and upper trailing arms. Colin Chapman tried this with the original Mk1 Lotus Cortinas too.
The problem with this is that the bottom of the axle has enormous forces (from your engine) trying to move it forward on acceleration. The top of the axle is in tension, thus with the standard Alfas setup the A-arm is in tension, while the lower trailing arms are in compression.
Thus my rear axle (not an Alfas) bent forward. Oops, but handling and grip was fantastic. Chapman also had this trouble and also rear axle leaks because of axle housing flexing, etc.
To solve this I added lower trailing arms, but to ensure full axle movement (for a single wheel bump, etc. and to keep the wheels on the road all the time ... ) I installed very soft rubber bushes in these lower trailing arms. Thus the rubber would flex and allow the axle to go where it wanted to a limit. This limit would stop the axle bending.
The traction and handling of this setup was the best beam axle setup I have ever driven.
The tradition problem with beam axles is that the roll centre is in the middle of the axle, and with most setups they are hopeless over a single wheel bump, ie. the whole car chassis moves with the bump not just the wheel/axle. This is because the axle movement is really just up and down, no angled to the chassis movement is possible (except for rubber flexing).
Alfa solved this BUT compromised on a very high roll centre that is no good for traction through corners ... thus they have to run the front of the car very stiff.
Note though that photos of GTA/GTAm's show the front wheels in the air but the rear wheels on the ground ... thus whatever they have done with the sliding block and axle location allows very good one wheel bump axle movement, and thus traction. Thus again who knows what other location they did on top of the sliding block???
Pete