I did not see any 1977 Dodge Tradesman steering components on
www.carsteering.com, but I might not have been looking in the right place
If it were me, I would start by obtaining a factory parts manual for your 1977 Dodge Tradesman and researching exactly what parts were different between Tradesmans equipped with power steering and Tradesmans equipped with manual steering. Once you have a list of part numbers you need, I recommend searching for new old stock parts warehouses and used part sources for those parts. I know of two good new old stock parts sources in the US-
Arizona Parts:
http://www.arizonaparts.comand
Old Car Parts Northwest:
1120 SW 16th St Ste 7,
Renton, Wa. 98031
Phone :206-300-1083
Parts like power steering gearboxes, power steering pumps, and power steering hoes can still be purchased new. I recommend
www.rockauto.com The pump brackets and pulleys will need to come from a junkyard vehicle but can be pulled from any Dodge smallblock engine that had power steering. The harder parts to find will be the steering column, but most Dodge vans had power steering so you might be able to find one of those in Europe.