There seems to be a glut of big framed bikes on eBay this week. Here's a nice Grand Sport Trek going for a fairly low price ($113) with one day to go.
I guessing the frame size from the pics and the straddle height, which is the only measurement given by seller. I'd also guess this is a late 77 or 78 bike due to the monochromatic paint. I've got the same frame in Ishwata tubing, and it's an excellent rider. Happy hunting.
Tom Adams, with too many big bikes already in Shrewsbury NJ