The suspention on the 125 and the 175 is the same. Many were lifted with a kit that was (still is) available that would lift the bike around 25MM without loss of travel. I have the very thing on mine, came with it i might add.
The blue 175 has the wrong front pipe that is most likely a gianelli expansion chamber. I have one on mine, good ones are rare the yellow 125 has the std unit. If they differ betwween the 125/75 its only on the inside.
The bottom end is identical bar the clutch which is a couple of plates down, the earlier bikes had a (paul will agree on this) monsterously restrictive airfilter set up that was thankfully massively revised from 80 onwards. That had the airfilter swapping sides with the oil tank.
The biggest diference is really the ignition as these may be points or CDI depending on year, there is also 2 options for the cdi but they are hardly visual.
To know for certain we need the engine/chassis number. Both if their different.
This should help for now
DT125MX production code 4J3 ,engine/chassis number 2A8-100101 onwards. june 79 to april 82
DT175MX production code 2K4 ,engine/chassis number 2K4-000101 onwards. feb 78 into 79
DT175MX production code 2X2 ,engine/chassis number 2K4-010101 onwards. during 79 only
DT175MX production code 4J4 ,engine/chassis number 2K4-020101 onwards. 79/80 to feb 85 , this model had the square section sw arm.(Which requires a diferent rear shock).
As a final point i agree with OG that front end is wrong, from the bars to the front wheel, including the instruments. Looks like an earlier front end from a twinshock if i had to say.