The trifecta of cheap, light, and wide aren't going to come together for this one deal in a short time frame.

Before pursuing it any further, I'd see what normal retail of the wide 16" tires is, as the rim size will lock you into it's use for the future. If the tires can be picked up at a reasonable price at normal retail, then it might be worth the expense of rims.

Cheap - used Crown Vic, Jeep, or Mustang but too narrow for a 295.
Light - Competition rims, but not necessarily not cheap if shipped.
Wide - Aftermarket, but necessarily cheap nor light.