Hails bells Buz,I remember when the big twin pans and shovels were 74 inches....the 84 inch strokers were considered unreliable behemoths. When the 80 inch shovels came out ,they kept making the 74s for a year cause some folk didnt trust the 80's. Course in the 40's you could buy a 61 or 74 inch "Big Twin" OHV knuckle(later pan) or a 74 or 80 inch big twin flathead. Big twin was strictly a term to differentiate from the 45 inch flatty. My uncle rode an 80 inch flatty into the 60's.....good maintenance and the damn thing was indestructible.