The brake levers look like they are probably the originals; although they do look ugly and cheap, suitable levers (ie not bendy or too long) were not thick on the ground back then and these were one of the few designs available.
They can't be the originals because, according to their website, the 'Promax' brand has only been around since the late 1980s. They also look as if when pulled, your fingers need to be on the outside so as not to get trapped between the lever and the grip. The Shimano XT levers are doglegged so as to leave a gap for the index and second finger. i.e. to hold on tight to the grips with the two inside fingers whilst braking with the outside ones.
The front gear cable arrangement is as it should be. On prototypes I used a full-length cable, which ran under the bottom bracket shell. However, this soon filled with water and the inner wire rusted. There were no top-run front mechs available back then, nor PTFE liners. I experimented with a little lever device to allow top-run. Considering that there were only two chainrings, and front-end shifts quite rare, running a bare wire under the shell, which has a thick polyester powder coating was, for the period, a good solution. Leave it as is, with the occasional addition of a little dab of thick grease.Interesting!
I have always run the front changer Bowden cable in a wide arc passing above the bottom bracket shell. I have never had any problems with water ingress and as you know, I do like the occasional ride in the mud.
9/16" Suntour BMX MP-1000 pedals / 56 tooth TA 6-bolt chainring.(I'm not bothered if the teeth are worn or damaged)