I've seen those "frankenstein" double cases, even considered getting/building one. but then I found the Strong Box and the cost difference was close enough that i would go with it instead. one problem i was having trouble getting around was where to put three additional shifters in the cab of a 89 cherokee. I'm still contemplating that one. a 7.13 double-low is so tempting. and with the 300, i would get 2-low, 2-double-low, and my choice of which axle is driven. ooh, they also make a 4:1 kit for the D300! 10.88:1 low!!!!