thanks Jerry, i spent some time today performing the tests you mentioned and also started exploring around under the truck
(prior to having the opportunity to read your reply)
my findings were exactly as you described, my particular setup was the "sliding clamp at the shifter arm " assembly.
i sprayed the clamp with some PB blaster and attempted adjustment, in the process (and this is embarrassing but i am still learning)
i discovered reverse is engaged by actually raising the shaft/shifter arm assembly via the "knuckle" type assembly at the base of the steering column. the good news is reverse does work, the bad news is the reverse "displacement" does not engage via the shifter arm, i have to physically pull the shifter shaft up while moving the shifter into the reverse position. any idea how to remedy that?
also the sliding clamp assembly was frozen up, i cleaned it with PB blaster and tightened it up well, its an odd setup, do these have a tendency to get loose over time?

i also noticed electronic wires/clips in the area, what role to these serve relevant to transmission/shifting operations?

thanks for the detailed explanation concerning conversion, i was under the impression a like donor truck would make things a bit easier. i guess i have more considerations to take into account.
my ultimate goal would be to have this truck setup reliably to take on the highway or a road-trip, i just dont know if that's feasible with the current original setup?