It is a bit difficult to diagnose your problem without pictures, but 101 tanks and frames are basically the same for the whole 101 series 28-31. Just details differ. Tanks can definitely be changed between year models and only -31 frame differs in the rear axle casting for all I know.
Have you checked that the downtubes are in straight line with the head casting! A head on accident can push in the head casting, and then the top tube is bowed up a bit so it doesn't follow the tank line perfectly. A fairly small accident can make a difference. The downtubes should be parallell, about 5mm gap in between on top, but the frames I have do close up a bit, to 3-4mm lower down where they bend outwards.
I haven't measured up my riding bike frame and fork in a jig, so I am not sure that bike is perfectly straight, but by eye the head casting and downtubes are straight in line and the top tube follow the tank line very well. There is just a small gap about a mm between the tank and casting at the front, and between the front fender and frame it is about 21-23mm, however that can differ slightly between bikes because the fender can be mounted a bit different. And I am a little bit suspicous about how straight that fork really is.
I wish we had access to a better drawing of the frame and bike measurements in the club! beacuse all frames and forks, doesn't matter if it is NewOldStock, barn fresh or second hand should be measured and thoroughly checked for any flaws before assembly!
My bike I suspect is running a bit like a crab, because I am not satisfied with the straight line stability and I have to cant the rear wheel slightly (or rather turn it by adjust the axle plates unequal) to get it going somewhat straight on the road.
