What are the differences in the "dash" in a model 65 with a 3" pistol. I have a 65-5, 3" but see other models like 65-3 also in 3"?
The number after the dash designates which 'modification' it is. Each subsequent number indicates some sort of engineering or production change. So, first was the 65, then the 65-1, 65-2, etc. There may be a "sticky" somewhere on the forum to explain them more fully. The dashes have nothing to do with the barrel length.
The S&W Model 65 ".357 Military & Police Heavy Barrel Stainless":
Apparently, there was no "no-dash" variant, according to the Standard Catalog of Smith & Wesson, 3rd Edition.
65-1 (1972): model introduced
65-2 (1977): move gas ring from yoke to cylinder
65-3 (1982): delete pinned barrel, delete recessed cylinder
65-4 (1988): new yoke retention system, floating hand, hammer nose bushing, radius stud package for the 4" square-butt
65-5 (1988): new yoke retention system, floating hand, hammer nose bushing, radius stud package for the 3" round-butt
1991: Model 65 "LadySmith" introduced with 3" barrel and shrouded ejector rod
1994: change extractor
1995-6: round-butt only, limited run of grooved grip-frame backstrap and frontstrap
1997: MIM trigger and thumb-piece
65-6 (1997): MIM hammer, frame-mounted firing pin
65-7 (2002): internal lock
65-8 (2005): Model 65 LadySmith with two-piece barrel
2005: Model 65 discontinued