Kinda hard question without details like heads. Depending on what else he gives you, shortblock is just the rotating assembly, so you'd need everything else. Intake, heads, valvecovers, ehaust, fuel system, accessory brackets, pulleys, etc.
I know I don't trust engines from CL after a few experiences. So I don't take their word, I would definitely inspect it. Look down the cylinder holes for crosshatching, no marring or glazing should be present. Make sure all pistons are the same color, ask a lot of questions, he may be able to tell you what power it put down with what heads, but again, take it for face value. I'd also pull a main and check the bearings, absolutely no copper should be visible.
Without a part # on the canton, I'm not sure. I've only seen 7qt canton road race pans, and they are tight. I'm sure you'll have to remove the factory 2 point lower brace and doubt anyone makes a 4 point lower brace that fits. It does need a special dipstick and tube, the stock dipstick hole needs to be plugged. For $800 I'd do your homework, my last $500 "25K mile shortblock" off CL lasted about 14 miles before it put a hole in the side of the block.
