Yes, Dunfermline did indeed beat Brechin 8-0 on that day in 1972, having led 6-0 at half time. I was there, but I don't recall (although the programme is somewhere) whether Jim Leishman was playing.
Never having seen the Pars rattle up a score like that before, I got greedy and wasn't chuffed there wee only 2 goals in the second half. So the tale below may well not be aporcryphal... :-)