Bicycle Mechanics - Junk singlespeed: uneven crank distance from chainstays?

Premise: I have lots of junked up parts, and not enough shifters. time to test frame single speed style.

frame: centurion le mans rs
crank arms: shimano 600 EX
bottom bracket: shimano un57 107mm, 68mm shell

Problem: I cannot for the life of me figure out why the non-drive side crank arm is only three millimeters away from the chainstay, while the drive side arm is a good centimeter away, if not more. The bottom bracket was installed correctly, and I've checked and re-checked the seating of the crank arms, just to be extra sure. Can anyone tell me why this would happen? Is it possible that the cranks require an asymmetrical spindle? to clarify, i'm talking about the pedal end of the crank, not the mounting point end of the arm. the arms are straight and have not been crashed/dented.

Additional problem: the crank spider seems to be uneven on the vertical plane; i've tried three different chainrings, and when mounted the rings waver left to right when seen from behind the bicycle. i've tried a bit of shimming, with little luck. are there any other solutions?

Thanks ahead of time.

sound like the right crankarm / spider is bent . the only repair is to replace it. or the chainstay (frame) is bent outward on the right side . some pictures or video would help to see what you doing.

is the right side chainline right ? left hardly matters. it clears the chainstay?
buy a different longer on the left end BB if it bothers you.
after all you said its a junque build up .
if It gets you down the road its a success.

just not a total success.

There has been a prior owner that hit the ground
with the pedal on the inside of a corner,
bent crank arm and spindle of pedal

to close out this thread, i actually ended up using a 110 bb, and the crank arms are now equidistant from the chain stays. have no clue why it was like that with the narrower bottom bracket.