Road spirits advice is good and we concur so won't add to that.
In Northern Chile we did NP Lauca and NP Volcan Isluga, we have 39 liters full and we nearly got caught short after filling up at Putre, even running at 4.5 - 5 L / 100 km that we did the fuel distances there are long, that is the only place I thought we were going to push the bike.
Uruguay we spent nearly three weeks there, flat, expensive and not really an adventure bikers paradise, nice beaches north so your coastal choice is good, plenty of camping along there, really nice camp behind Fortaleza.
Free camping, you can easy enough in the middle but it is just an expanse of farmland and not a much shelter, we camped in Durazno, free camping there with toilets and HOT showers.
Really cool camp ground 10 k north of Colonia too right on the river.
While we had an ok time in Uruguay we found it a little empty after Arg, Bolivia and Chile, not putting it down but knowing where you have been it does not have the adventure or scenery side.
Uruguay things to do, Colonia, Montevideo.. because, Casa Pueblo, Punta Del Este, Punta De Diablo, Fortaleza, in the middle there is not much, there are hills in the north but we did not go to there.
Paraguay we only went in at Ciudad Del Este, noisy stinking town, other bikers who have gone in said not worth the money they paid for a VISA but I don't know on that as we only went 11km in (undercover

)...for what we saw and what others say I wouldn't put Paraguay on the top of the list unless you want to tick off countries.
Foz Do Iguassu, although touristy it is well worth the visit, we did both Argentina and Brasil side, Argie side we took the boat with the rest of the sheep but I have to say I enjoyed being a tourist for a day despite the crowds for something so spectacular, both sides are worthwhile IMO.
Hope this helps, any specific questions on Uruguay let us know and will see if we can answer.
Cheers Andi