Yes. But mostly because I've found that I really don't need as large of a toolbox as this combo has. I'd rather have a larger tank and a smaller toolbox. It kind of depends on which is more important to you.
I have the RDS model 72775 tank/toolbox combo.
Exterior dimensions are 55 (length) x 20 (width) x 19 (height)
If I was to do it all over again, I would get their model 72743 which has the same exact overall dimensions, and has a fuel capacity of 60 gallons but with a decreased tool box height from 10 inches to 6 1/4 inches. Length and width of the toolbox is the same on both.
There are many choices at the RDS site. And I read somewhere that they will even make one to your specs, but have not confirmed this.
The main reason I chose this particular model (either 72775 or 72743) is because the total height is lower (barely) then the top of the bedrail and I want to be able to put a full cover over the box and the hitch (when not in use). I think that a tank that is even 1 inch taller will stick out above the rail cap, but I'm not sure - you might do some measuring if it matters to you.