It was from such areas that the Argentine Indians, commonly referred to as coyas, and the mixed-blood cabezitas negras ("little black heads") fled in steadily increasing numbers, pouring into the cities in search of work and setting up shantytowns like the one in front of the Guevaras' home in Cordoba. From their ranks came domestic servants such as La Negra Cabrera and Sabina Portugal, and the cheap labor force for Argentina's new industries and public works projects. Theirs was the despised social class Peron had appealed to when he called upon the nation to incorporate the descamisados, whose noisome presence and clamor so irritated the white elites in their once-exclusive metropolitan idylls.
(Jon Lee Anderson; Che Guevara: A Revolutionary Life)
Have I understood it correctly that the descamisados were not really part of the nation, but rather like 'servants', and so Peron called upon the nation to 'absorb, embody' them, as it were, so that they could become integral part of the nation, so to say.
From a bit of quick research, it appears that the descamisados (shirtless ones) were the working class poor of Argentina and would have probably included many of the indigenous Argentinian indians. As such, it would have been the (ex-European) whites who were not part of the original inhabitants of Argentina.
Because of their numbers and his promotion of their cause, it would have been comparatively easy for Peron to recruit and use them as his power base. In return he could offer them the possibility of freedom from oppression and, as you suggest, reabsorption into the new nation.
Hope this helps