As I recall 1st gear is usless... like 6.XX:1. It's HUGE. I don't think it'd fit without some trans tunnel mods or a bodylift. They're also pretty spendy if you can get one.

Why can't you tow with a T56? It's a good close ratio unit... with 30" tires and a 4.88:1 you'd be around 2100rpm @ 70mph in 6th as it has 0.50:1 OD I recall.