in tank sending unit pickup module

[ken527]

I never thought it would be this difficult finding the correct sending unit for my truck so I am asking for some help identifying the tank connections.
My 2007 LBZ Classic CCSB has 4 hose connections. Supply, return, vent and one connection that looks like it is just capped off, which is the one that confuses me.
If its just capped off I could have used it for the AirDog return line. If its a relief or check valve I need to leave it alone.
Still looking for replacement, some sending units have 3 hose ports (MU 1574) and some have 4 like mine (MU 1228). If I don't need the 4th port I can buy one with 3 connections for less than 1/2 the cost of the one with 4 connections.
Some sites list either one as correct for my truck and a call to my local chevy dealer parts department using my VIN number to look it up and he tells me he has it for $382.14 but won't give me the right part number so I can verify which one to buy or which one I will be getting.
So have a look and if you can tell me anything about the connections and if the 3 port unit will work?
Thanks you,
Ken

mine looks like this one:
http://www.ebay.com/itm/04-05-06-07...Silverado+2500+HD&hash=item27dffd384d&vxp=mtr

http://www.ebay.com/itm/MU1574-ACDe...Parts_Accessories&hash=item3cdff716d9&vxp=mtr

http://www.ebay.com/itm/Fuel-Pump-a...Parts_Accessories&hash=item338ff4214b&vxp=mtr

I just noticed a difference, the return line in MU1574 does not have the tube from the return line down to the pick up cup.
The MU1228 has both tubes extended to the pick up cup.

 

[NAFLASH]

The sending unit has nothing to do with the pickup assembly. Go on rock auto and order the sending unit for ~$60. It just clips on the side of the basket.

 

[ken527]

Thanks,
But its the whole assembly I need. Mine got pretty crusty and I roughed it up getting it out.
Trying to fine the right one.

 

[NAFLASH]

Oh wow. I understand. Rock auto lists 2 for the 2007 classic and one for the 2006 year model. I would purchase the one that is listed for both year model trucks because they are identical. It's $192

 

[ken527]

Thanks,
I will try that route.

 

[ken527]

Does any one know if that 4th port that is capped off, is it just a roll over valve to keep liquid fuel from traveling up that line to the charcoal canister on Gas trucks? Maybe it allows the condensed gas from vapor flow back to the tank? (capped off because diesels don't use it)
If it is, I am thinking its the same kind of valve RDS uses on there aux fuel thanks use to fill the main tank at the filler neck. It would be a great location to gravity feed the main tank from the aux tank in the bed.
Need to know more about that port does any one know?
Thanks,

 

[NAFLASH]

I can't answer for sure but the gas a diesel sending units are nearly identical if not exactly. As long as you can plug in the 1/2" supply and 3/8" return.