Toyo pickup trouble

i have an 86 toyo pickup and am trying to sell it.
this weekend i took it for a spin and it ran fine. today i went to move it
and its struggling to move. it appears that the left rear wheel is locked up
sort of. it was a little warm today around 60 degrees. when it cooled off
this evening i went out and it ran better, not near as "draggy"

is this the rear end or perhaps the brake drum is locked up?

please let me know

chaz