Hi,
The W-series Crew Cab ( GMC-Isuzu-Chevy) come in 2 sizes... a 4500 @14,500GVWR and a 5500 @17,950 GVWR..both can support a 16' Dry freight box....(max)
The 4500 (Isuzu badge NPR-HD) will have 16" rims
The 5500 ( Isuzu badge NQR) will have 19.5" rims..
Both trucks have a I-4 turbocharged...