So went out and bought a new fuel pump for my 2005 ram 1500 it's for a 34 gallon tank but I think my truck as a 35 gal tank will the pump work ??

Get a build sheet for your truck from here. It will tell you what size you tank is.

I thought all gassers had 26 gal?

Correct me if I'm wrong, but I think there were some instances where bigger tanks could be equipped.

Granted, mine is a second gen, but, it's an quad cab, shortbed, with a 34 gallon tank. I also have the 8.0 though..... and god knows those things SUCK gas......

26, 34 & 35 were all available depending on bed length, 1550 or HD, etc. This is from 2003:
52102505AB - 34 gal 2500/3500 (they were up to 'F' revision before discontinuing)
52102510AC - 26 gal 1500 (they were up to 'E' revision before discontinuing)
52102511AC - 35 gal 1500 - 3.7, 4.7, 360 specific
52102585AB - 34 gal diesel 2500/3500 (they were up to 'F' revision before discontinuing)
52102588AB - 35 gal diesel 2500/3500
52121149AB - 35 gal for V10 & hemi 2500/3500


I find it funny that there was an available 35 gal for the little engines in the 1500 but not the 5.7. Things got much more simple by 2004. I didn't include the 2005 because they split the 1500 and HD's into different parts books that year. I added it below for your viewing pleasure.

Try searching a Mopar site by VIN to see what pump it comes up with. That might give you a part number you can cross ref with the one you bought.

I'd recommend getting the correct part number for a replacement fuel pump. It's a once every 100k miles job so doing it right save aggravation.
If you are asking, "I've got the wrong fuel pump, but can I use it anyway?" You'd need to see how it fits. The plumbing and harness will fit. But problem could occur if the pump base does not fit properly into the form of the fuel tank. You may also get an inaccurate fuel reading if pump is not seated properly.