Just swap the shifters doesn't work. Its a 7 speed freewheel. Swapping the shifters is a whole drive train ordeal, including wheels. I'd essentially be reusing nothing but the frame. Its not a quality enough frame do do that with.
I don't understand - friction stem shifters shouldn't be any different than frictional downtube shifters...? They should shift just fine across just about any freewheel or cassette you have. Pull the old shifters and cables/housing off, install new shifters and housing, check cable tension - done.
It doesn't really matter though, that was just my take. There's a lot of ways to ride
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