They should. Encore are just straight up reissues of the old figures without any mold changes that I'm aware of.
Do they or don't they? I have both Ratchet and Ironhide though they're vintage, is there any difference between the encore ones and the vintage ones?
They really don't fit on G1 that well. I put one on my G1 Ratchet and the fit is not good in vehicle mode. They were made for the Encore molds apparently(there is obviously a very slight mold difference between G1 and Encore) and they fit on both of my Encore versions very well. You won't have much problems in robot mode(the fit is fine for that) but once you change into vehicle mode you will see what I'm talking about.