After a bunch more searching I figured out that the leftward bound hose goes to the filler tube. The filler tube is different on the 04-06 tanks.

I went to a different yard from before. A wrecking yard that will actually let you pull your own parts. I intended to just grab a filler tube, but the evap was just laying in the cab so I grabbed it as well. Here's what $20 got me.



I'm not sure if I'll use the charcoal canister or not, but at least I have that option now.

 

Use the filler tube from your 99 tank. Run the largest vent that you can so it won’t take forever to fill up at the gas station., if you’re Changing sending units(because you have to if You swap tanks to use the bigger bucket), you will need to reflash the PCM with the fuel tank PWM gauge table values flipped. Otherwise, the gauge will read backwards.

I remember also having an issue with the vents and routing for the purge solenoids were somewhat different. I think I ended up bypassing the line for the tip over valve to prevent the dreaded 30 minute long refills at the gas station.


in the end, I ended up tapping a 8an or 10an bung for my feed and used the stock feed for return.

 

When you guys did the swap did your tank hit the cab of the tank in the front?

 

It did not.

 

hey I’m also doing a gas tank and pump swap I have a 2003 GMC and I’m putting a 2005 GMC gas tank and fuel pump and evap form the 05 my question is where did you put the fuel return or did you get rid of it? And is there any other problems I will run into thanks