Fresh ish? I know a butcher so they'd be like a week old or so, so probably enough to mess with it a bit but not unduly. Or I could use green Oak wood I suppose.
I would like to, yes, cuz that's a weird property of blunt trauma. Stabbing or slashing is readily apparent just off of depth of the cut, but I'd need like water balloons of something inside. Probably some reasonably durable surgical tubing or something filled with a liquid.
Honestly not sure how to properly fake an organ.