If you're putting in a 350, you could use the GM S6-650 6-speed manual that they put behind the Chevy Duramax and 8.1L. It has like a 5.75 granny low, and an overdrive of .72. This transmission also has a PTO attach built into it.
Bellhousing is the traditional
Chevy (at least for the 8.1L). This is a high towing capacity trans,,, it gives you the low and the high. I think they go for about $1800 or so new. You could probably pick on up cheaper used though. Actual gear ratios are:
1 2 3 4 5 6 R
5.79 3.31 2.10 1.31 1.00 0.72 5.23
