I would bet that the hose barbs on the engine are 5/8" hose. Some vehicles use 5/8" for one hose and 3/4" for the other, our older trucks are probably the same size for each hose.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy