Yeah, a lot of people don't know that 4/5/1972 was actually a mini-outbreak as well. There were two more F2s in the Columbia Basin and then another F3 that day near Creston, WA. The wind shear over the region was just off the charts that day, and there was sufficient enough surface heating/steep enough lapse rates for some pretty huge updrafts to form with the main squall line and take on supercell characteristics.
That line also produced golf ball sized hail and 60-70mph straight line winds in places throughout the Portland metro, so even without the tornadoes it was a pretty historic event around here.