Can you take a speedometer from a 1995 peterbilt 377 and put it into a 1997 peterbilt 377?

Method of actuation would determine whether or not it would be worthwhile to do this. You're talking about model years in which the speedometers were not yet controlled by the ECM, and, therefore, relied on gears in the speedometer to gauge speed. So, if your 95 has, say, a .74 overdrive transmission and 3.55 rears, and your 97 had, say, a 1:1 transmssion and 2.64 rears, the speedometer from the 95 won't be accurate for the 97.