So, does anyone have any thoughts on this? It's worth noting Spain was still suffering from autarky and was still barely getting out of international isolation.
Luis Carrero Blanco is still alive, as he wasn't assassinated until 1973, so he is the natural successor and the one that Franco wanted. So the succession is relatively easy, although a Carlist King is likely to be crowned sometime in the 1950s as there is no Unification Degree by Franco and associated purges of Royalists. Until that point the Carlists, since the 1930s, had been extremely powerful and influential, with a strong financial base, armed wing, and youth as well as women's groups; this would also help to give the regime more legitimacy and power, instead of leaving it as a personality cult dedicated solely to Franco.
Economics is, however, much trickery to speculate upon. For one, I don't know what Blanco thought about Franco's economic policies, with the latter only moving from autarky in 1956. Doing so in 1948 is obviously better for not just the regime but also Spain, because by the OTL 1960s Spain was absolutely booming to the extent
it was speculated that Fascism would make a come-back based upon the success of the Spanish Model:
The biggest success was the acquisition of needed capital. The end of autarky brought in roughly $8 billion worth of foreign direct investment. Increased tourism, twenty million visitors came to Spain, and remittances from abroad supplied funds for needed capital goods. The new policies and flood of money into Spain from abroad fueled a fifteen-year growth in the economy, from $12 billion to $76 billion, that was surpassed only by Japan.
The economic transformation was so powerful that some thought it gave fascism a new lease on life. In an October 7, 1968 editorial entitled “Fascism for the Future,” the American historian Gabriel Jackson speculated that fascism would outlive Franco. As he wrote, “a Fraquist type of dictatorship may continue for decades in Spain and by doing so may provide a model for other nations that achieve a minimum of economic prosperity in the absence of strong traditions of political liberty.”
To get an idea of how much of an effect no autarky and earlier Marshall Aid funding would have:
This article uses historical fact as a natural experiment to measure a country’s welfare loss from shifting from an allowed to a restricted trade situation, based on international trade theory. A welfare loss of 8 per cent of GDP is found. The evolution of domestic import and export prices in Spain in 1940–58 fits international trade theory assumptions. The main years of autarky are not those commonly considered, but 1947–55, marked by the exclusion of Spain from the Marshall Plan and the Madrid Treaty between Franco’s regime and the US. The upper-bound welfare loss for 1947–55 is 26 per cent of GDP.
A booming Spain from the late 1940s on, instead of a late start in the 1960s, might be sufficient to place it firmly on the same level as the UK or France; i.e. a $2 Trillion + economy. I wouldn't be surprised if "Francoist" Spain is able to last until the present given this, in the same way the PRC has outlived the collapse of Global Communism. The question is, however, whether the support/political ability to do such was there, by Blanco and the various factions in the regime.