the transmission undertray on my mk2 SE has rusted away on one side and has started hanging down, so it needs replacing.
I’ve found someone selling a part that looks right, but is off a mark 1. Is this part the same/interchangeable between mk1 and mk2?
Not sure which you mean? is it a heat sheild? The front undertray is plastic
I dont think they are the same .Either way most cars dont have a gearbox tray still fitted but we have correct type if you really need it.My advice remove it totally.
I did look under a similar age car to mine and it didn’t have one, so is this not important?
If you really want to fit one use the Mk2.5 one which is an effective tunnel brace