i built a 240 gal. plywood tank with plans similiar too garf's. I think you would save money if if you could get the glass fairly cheap. My tank is 8 feet long and 24 inches tall. The glass is about 94 inches by 22 by 3/8. I had the edges rounded so that cost a little more. With delivery it cost me almost $300 for the glass. I think i could of probably found something cheaper. The wood was about 40 bucks. Screws, liquid nails, and silicone was pretty cheap. I coated the inside with a epoxy from aquatico.com, for about 60 bucks. The gallon of epoxy was enough for my 8 foot tank. You would have to do the math for price comparison for a 140. If you need a custom size tank shape then plywood may be the way to go.
Good luck,
Shawn