Gen Hatcher can probably be considered "somebody who really knows" about this topic.
Chapter IX of Hatcher's Notebook (a copy of which everyone really should have) is "Receiver Steels and Heat Treatment", and goes into the history of the problem, the investigations, and the conclusions drawn. As noted by varg above, Rock Island receivers above about 285,507 are considered safe because they have the revised heat treatment.
While the entire chapter is well worth reading (especially for those who own a low number receiver), the semi-TLDR crux is that the Board convened to look at this issue determined that these low-number receivers should be withdrawn from service and scrapped, and that they could not be "fixed" by re-heat treating: the steel was over-heated and "burnt" in the original heat treat.
It is worth noting that, in the catastrophic failures, the receivers gave way with the barrels undamaged. A rebarrelled low-number receiver is no safer than one with its original barrel, and might even (as Makarov noted) be more likely to fail due to the stresses of rebarrelling.
Were it my rifle, it would either be a wall hanger or be restricted to low-velocity cast bullet plinking loads.