Trek chainline question.

Somerset Pedaller

Retro Newbie
I am rebulding a '93 Trek Composite. The largest chainwheel pretty much lines up with the smallest gear at the wheel, so the smallest chainwheel lines up with the 4/5 gears. Is this normal? I was expecting the middle chainwheel to line up with the middle of the cassette. I am wondering if I should fit a shorter bottom bracket, currently 127mm. I am fitting a Mountain LX crankset which is a couple of teeth bigger than the original and the clearance between the small sprocket and the frame is only about 6mm, so not much to play with. It's difficult to get a decent picture of this. I have shown it from the crank end and the wheel end, as well as the frame clearance. I used a straight edge to check the allignment.
 

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