I get guys closing the gap on me all the time, mostly tradie utes, vans and LDV truckies are the most homicidal. The B-doubles seem more laid back than the smaller guys.
That said, you get all kinds in all vehicles, so I just assess each vehicle every time before I pass. Sometimes I ignore them once I past, and sometimes I give them a friendly wave (not the one finger salute either).
Threading the needle in situations like these is never fun, but sometimes with the ones that are really out to kill you, when they move suddenly at the last possible moment, going through with it is the only option.