In Look to the West, Portugal's fortune in the 18th century has been somewhat happier than OTL's. Initially there were few changes to the events of OTL, but real divergences began with the 1750s. Spain and Portugal signed the Treaty of Madrid to demarcate colonial zones in 1750, and then embarked on the Guarani War as allies much like OTL.
However, because the Third War of Supremacy ended in 1759, unlike OTL's Seven Years' War, the eventual Hispano/Anglo-Portuguese conflict (the First Platinean War) starting in 1763 remained separate from a greater European war. British army assistance in Portugal against Spain showed up serious flaws in the Portuguese army (typified by the defeat at Badajoz in 1765), leading to reforms that in OTL would not happen until the Peninsular War.
More significantly, the Portuguese response to the Great Lisbon Earthquake of 1755 has been more coherent in TTL. The mad Queen Maria was declared insane and succeeded by her son as Peter IV in 1787, who created a policy of expanding colonial trading operations to finance the earthquake repairs. This was also helped by his seizing the estates of rebellious nobles, further centralising royal power in Portugal, but he also revived the Portuguese Cortes, giving commoners more of a say and further weakening the nobles' power. This helped prevent much Revolutionary sympathy in Portugal during the Jacobin Wars.
The rejuvenated Portuguese East India Company has expanded its control further into India, virtually subordinating the Peshwa of the Marathas (helped by Maratha setbacks in other areas) and has formed a strategic alliance with Zand-ruled Persia.
1706-1750: John V
1750-1769: Joseph I
1769-1786: Maria I and Peter III (co-monarchs)
1787-1787: Maria I ruling alone (in name only due to insanity for most of the year)
1787-1821: Peter IV
1821-1851: John VI
1704-1736: Diogo de Mendonça Corte Real
1736-1747: João da Mota e Silva, Cardeal da Mota
1747-1749: Marco António de Azevedo Coutinho
1749-1750: Frei Gaspar da Encarnação
1750-1769: Sebastião José de Carvalho e Melo
1769-1784: (several favourites of Maria I, changing in quite rapid succession)
1784-1788: Martinho de Melo e Castro
1788-: Nuno Caetano Álvares Pereira de Melo, Duque de Cadaval