I tried google and got 15.9k hits... Better bet is used, so I tried car-part.com web site.
Search: '1986 ford ranger harmonic balancer'
In the SE region, there were 9 hits. Dunno where you are. so...
$80 to $50, and some ??? (CALL) so you have a range.
From observation, if you did get a Dorman, I'd suggest you check the depth, width of the grooves if you have serpentine belt application. They may be too shallow, wide, thin, etc., but you won't know until you eat a few belts if they are and by then you are stuck with it.
tom