Why not use a PowerGlide as originally used and save the cost of the adaptor. The PS/Generator setup was original to cars of that era and that would not only get you what you want but would keep it original as well. I'm not sure if PS was offered on the pickups or not. Frankly I doubt it but the parts would still work on your engine.
A Hydramatic was also used in that time frame for pickups. You don't say if your truck is a first or second series 55. The second series would make more sense perhaps.
The 'Glide was never used in the Task Force trucks, only the Hydramatic. Power steering was an option, using the generator mounted pump and hydraulic cylinder on the axle. It is available reproduction, but is very pricey ($700 last time I checked for just the controls, hoses, and cylinder, no pump).
