I have an old Arneson/Twin disc 17-20 in-line surface drive (no drop box or ratio change). It is the predecessor to the current ASD 6 drive and carries the same spec according to Arneson. Should be able to handle up to 650lb-ft of torque just like the ASD 6. The main difference I find are the transom mounting on the 6 is 6 bolt as opposed to 4 bolt and the propshaft is smaller and different spline count. But the smaller propshaft is not a bad thing as I figured out that fat shaft and Bravo II props fit on the old 17-20 drive. The drive is without hydraulics but would sell the trim cylinder for the the right price. A steering cylinder from arneson is about $750.
Anyhow I found a NOS replacment drive and wanted to see if their is any interest in my old drive.