There is something amiss here
First are we talking the same truck Im thinking a flat deck or box truck
https://en.wikipedia.org/wiki/Isuzu_Elf but I see a van version exists.
What size wheels and tyres do you have now. Are you sure you cant get them in a Dot rated tyre.
Because its truck based it has much bigger brakes and susspension so going down to a 16 inch rim might not work Typically trucks have 18 to 20 inch rims
A photo of your truck might help
Sanding your knuckles before starting work can help. That way you cant skin them