Well after I posted this I did some research at the railroad. Truth is, the bridge base and the extensions I planned to use were made by (at least branded) Atlas, the side girders were cast with TYCO at the bottom middle. The Atlas Code 100 track fits perfectly in the area they designed for it, but the PECO and ATLAS Code 83 is about 1/32nd to 1/16th too wide. I may just use Code 100 in this part of the track as it is about 1 foot and a half of track involved times 2 (main line and siding), or I may crank up the electric sander with some 80 grit on it and cut 'um down to size. I will furnish a picture when it I get there. Thanks for the reply's.