I encountered two cases of the camshaft seizing on B21A engines in the mid 1980s (fortunately non-interference engines) and both were due to blocked oilways. after clearing the oilways as described, I carefully scraped off the metal that had adhered to the camshaft where one of the bearings had seized and scraped off any high spots on the bearing surfaces on the cylinder head and bearing cap.
I then used some metal polish, Brasso, if memory serves me right, on the bearing and replacing the shaft and bearing caps, wound the shaft through a few turns to effectively lap the bearing surface. Since it was a non-interference engine you could do this without the valves hitting the pistons. I then cleaned off all the Brasso and put it all back together. I felt it was a bit of a bodge job but since we'd paid virtually nothing for the car I didn't feel it justified anything better. It ran quite happily for years afterwards.
I did exactly the same with another car with similarly successful results. In each case the failure was due to poor servicing and probably cheap oil too.
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