have you got the right dipstick sump combo?
my first cossie engine failure was caused by a previous owner having the wrong combo-205 block 4wd sump on a poorly done conversion
full on the stick was just over half of what was needed...it packed in a day or so after i bought it-which was a pity as i only bought it to convert back to 2wd

but having had the car you would probably notice if under 3 litres took it to the top of the stick

i suppose it could have been starved of oil after/during a spin.. but the shell/journal furthest from the pump flow normally suffers first from starvation
ends being worn badly too
is the oil pump drive still very good/no wear also?