Personally I would not downgrade from a Shimano Freehub hub to a freewheel hub. 7 speed freewheels are magnets for bent/broken axles. It's not a question of if, it's a question of when. I'm 130lbs and I've bent them before. It's a poor design, a design the Freehub replaced. You could probably get your original hub built into a new wheel with new spokes for around $70.
$25 rim:
http://www.ebay.com/itm/NEW-Sun-Rims...item5890c9cd5f
Figure $30 for spokes. $10 for a spoke wrench if you want to try building it yourself, ??? for how much the LBS would charge you.