I have an aluminum gravity-feed 51 gallon RDS combo fuel tk and tool box in my 09 GMC 2500 D/A. I love the tool storage in the upper part, as well as the xtra 51 gallon capacity if needed. Just finished an 8000 mi trip through 13 states. This tank works great, no need to invest xtra in a pump (that someone may decide they need more than you). I Purch this tank from Northern Tool for approx $650 total several years ago.
.....To the others who are having trouble with slow drainage, check the breather tube that is connected to outlet of valve, mine had a dirt-daubber nest in the bend of the tube that I could not see, (until I removed the tube). I now screw a cap over the line when I finish draining. I fills my truck faster than I burn.