I have seen only steel inverted flair on all the GM trucks, although I haven't worked on anything older than my '57. My '55 International Harvester has steel line with compression on both ends but it's gravity feed from the tank to the carb.

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