I have a new gas tank and i have questions

[hoopty-cuztom]

ive been trying to get this truck to where i can just drive it for months now.
i do not have a original gas tank to look at, ive been using a 5 gal gas can in the truck to move it around,

i ordered a new poly tank from gmcpauls its a MTS tank, i have been searching to see what i can find about installing it im not having much luck,
what kinda problems am i gonna have?
and it has 3 brass fittings am i suppose to have 3 hoses for them?
and the small hose that comes from the filler neck where is it suppose to go?
my exhaust is gonna be very close to the tank. it says on the tank the exhaust can not be within 3 inches from the tank so i guess im gonna have to cut it behind the mufflers and turn it out or down

i thought this was gonna be the easy part,lol

thanks for any help