Hey JB welcome to the Stovebolt. I drive past Woodland frequently. I had family stuff in Portland last weekend, next weekend I plan to attend the swap meet in Canby and will drive right past you to get there. Then both the following weekends I'm headed past.
Task Force trucks are the second '55 and on through '59 Chevrolets. GMC's were called Blue Chip I think.
A '62 transmission is going to require an open driveline, and the modifications to change it to support a closed driveline would not be worth the trouble.
I would suggest dealing with the axle mounting first. The torque-tube type axle pivots at the springs and on a closed driveline you need to have it firmly mounted to the springs. One common approach is to replace the torque tube differential with one from a TF that will work in your axle housing, but was designed for open driveline. Then simply weld the pivots solid to hold the axle in place.
If it were mine I'd swap the entire TF axle assembly instead of welding the brackets, but its your choice.
I don't know if a TF driveshaft is the correct length or not. Any competent machine shop can make a driveshaft to fit, though there are shops that specialize in it. I can name one in the Seattle area but I'm sure a Vancouver or Portland shop would be better for you.
I don't know which member already did this, but learn to use the search function and while you are digging through stuff that isn't quite what you wanted you'll also find lots of useful stuff.
