I dont think the subframes are actually the same, but they are the same height
I always forget when i climb into my mates mk2 its quite a fall if you arn't prepared
edit: oh and another thing, if you have pre-90 MK2 GTI seats and want em lower without having to change/loose the std pattern, you can use a MK3 Polo GT/G40 (i.e. one with bolsters) driver seat base frame, it fits all the pre-90 MK2 fabric/foam perfectly and is lower
If you dont have bolsters a low spec Polo MK3 base will do, or you could get a low end spec seat and chop/weld your old bolster frame to it. Some late MK2 polo bases may work, but I think they have the forward/back handle on the wrong side a la MK1.
And make sure its a height adjustible frame, the non height adjust ones have the rear legs at the wrong angle to fit a MK2 well, I had one on my MK2 for a while (was from a LHD polo GTpassenger seat) I bent the legs so the seat would fit but it didnt slide in the rails very well.
