Hi guys! Let me preface this post by saying, dimension-wise, the 1999-2000 Yukon pump assembly fits my application, so that's the bar I've set.

However, I do not know too much about the GM/Delphi fuel pump assemblies. I am using an L33, with the stock truck manifold, and I would like to keep the stock fuel rails, which seem to be returnless. So I have a couple questions for you guys who I assume are much more well versed than me with these things!

1) A 2006 fuel pump assembly for returnless. I can't find any filter listing for the donor truck. Is the filter built into the pump? Is there no external filter?
b) The 1999-2000 seems to have a fuel pump listed for it. While I cannot find one for the 2006. But the pumps don't look so different externally that I am led to believe there is a whole extra filter assembly in the 2006?

2) Is the fuel regulator built into the assembly for a 2006? What about the earlier 99-2000?

3) There are no more or less fittings on a returnless unit than a return assembly. How does a returnless "return" the fuel? I always assumed there was an external filter near the assembly with a Y fitting, where it returned to tank. I believe I am wrong. Can't seem to find any good write ups on it?

4) (Long shot), are the dimensions the same? The pressures look slightly different, so if there is no external regulators, that could make a difference and I should go with a 2006 assembly, if the dimensions are the same?

5) Do the returnless systems just continuously pump and some goes back to the tank immediately? Or do they work via PWM and only pump what is necessary (avoiding deadheading with the PWM signal). Or am I giving too much credit to these fuel systems?

But yes, just a little confused on the GM return vs . returnless, and thinking I would like to go returnless since it's 1 less line, as well as I already have the rails!

Thanks guys, I appreciate it!