Welcome aboard wiley. Well, there's 2 ways around this; 1, find a 3rd member from a '68-'72 3/4 ton Chevy with the 350/automatic combo. Those tend to have a 4.10 ratio. There is also a VERY RARE '72 variant that is a 3.55 gear, but those are virtually impossible to fins (I've only ever seen one). Option #2, swap the entire rearend to a late 70s-early 90s Dodge or Ford 3/4 ton van Dana 60, the width is just about right and they are 8 lug. 3.55 is the common ratio on those, but most are also semi-float, so you may give up strength if use that version. I have also heard that the 14 bolt from a '70s-'95 Chevy Van is the right width, too. You'll have to seek out tha 1 ton van for that, not sure of the common ratio on those.
