You mean about storing the car in Paraguay or selling?
You get a 3 month permit for the car when entering in Paraguay. Up to a 12 month in Uruguay. and depending what you do when entering Brazil it can be eternally as you can enter through e.g Foz without applying for a permit . No policeman knows that you officially need a permit as the mercosulmembers do nót need one they think this counts for other countries too. We had our dutch registered Landcruiser for years this way in (and out) Brazil
Don´t know the size of your car, if it is under 250 cm height you can enter through our entrancegate and you are welcome to leave it here ( we live in Bombinhas, SC, just north of Florianopolis ).
If your question was about selling, well in Paraguay they import anything. am sure there will be quite some bureaucratical steps top be taken. Or you sell it , ofcourse a bit underpriced to a local who is prepared to do that later. at least it is possible. in Brazil it is not.