It looks I might be picking up a 1957 GMC 270 or it might be a 370 ( I can't beat the price). I don't know to much about this vintage or their model numbers.
1. What was the 270 or 370 series rated for?
2. What other vintage and series interchange parts wise?

1937 Chevy (converted to 4x4)
1942 Chevy G506 1.5 ton 4x4
1958 Mack B model (on Chevy 1 ton 4x4 frame)
1969 Dodge Charger
1987 K30 Crewcab