you could use a GM Dana 20 behind the 465, just have to get the adapter and transfer case from an early K5, and downgrade to 10 spline, and its pass drop. Don't think any aftermarket places know this exists, so I am unsure if the 3.15:1 gears will work in it.
If we really want to get nutty with crawl ratios, use an Sm420, Doubler with WMS 3:1 NP203 and LoMax 3:1 NP205, and axles with 7.17 gears. Give or take 450...lol