Singlespeed & Fixed Gear - new cranks help, please

im currently riding with a truvatuv cheap crankset which works fine, but i have a new 105 crankset sitting in my basement because i put dura ace on my road machine. the 105 has outboard bearings and i want to take off all but the 39 tooth chainring and use it on my fixie because i hate seeing such a good crankset go to waste. the problem is, a few reputable bike shops have told me that it cant be done because the outboard bearings will screw with the chainline. but, today, when im buying tires, i come across this http://www.ride-track.com/buy/TruVativ-Omnium-Track-Crankset/20280005/ ... apparently truvativ now makes an outboard bearing crankset for track. i have the same BB for my 105 as the truvatuv crank on that site uses, so it made me wonder, is it possible to use my 105 on my track frame or are the bike shops right? thanks.

Just try it out if you have all the parts.How long does it take to change a crank...10min?

outboard bearings don't screw with the chainline per se, it's just that the chainline isn't adjustable by simply using a different length bottom bracket.
That Truvativ crank, presumably was designed to give a 42mm chainline.
Road double cranks usually position the inner ring at ~39mm and the outer at 45mm. (i've never owned a crank with external BB cups, so i don't know if this convention is still the case) In the days of square taper cranks, you could adjust chainline by simple changing your BB spindle length. However, since on your 105's the spindle is essentially integrated into the cranks themselves you have no way of repositioning your chainrings relative to the centerline of the frame.

Now you can still work with this.
You have to install your cranks and measure the chainline of the inner and outer rings. Maybe you'll get luck and one of them will be 42mm. Otherwise you'll have to make all your adjustments to your chainline at your rear hub.

what if i used spacers on the chainring bolts to somehow space it to the right spacing? i dont know exactly what im asking here, but like if i used larger chainring bolts and found some small washers and evenly spaced them so that the chainline was 42mm.

chainring spacers will only allow you to move the inner ring inwards, or the outer ring outwards
since the inner ring is already too far in, and the outer ring is already too far out, then chainring spacers will be useless

hmm, i see. maybe i should clarify my POV. i wanted to remove all but one chainring from the crankset, then, if needed, use my makeshift spacing idea to try and make the alignment workable. does this sound feasible?

also, on sheldon browns site/ the harris cyclery i found these, would they work well at spacing the chainring right (at 42 mm i think) so that the chainline would be straight. i have all the chainrings off my crank and i cleaned and repacked the bearings, its just dieing to be put on my fixie.
3 mm Chainwheel Spacers