Looks like you now have some direction with which to head - that's a good thing.
$100 is fine. The catcher looks to be good, and don't go changing the reel or knife until you've had a good look and even post more photos here as you'll get some good opinions about their current status.
Searching the forums where units are being restored will give you plenty of answers on engine choices. B&S are decent, but theres more discussion around the Honda and Chonda options for their smoother operation.
I guess the first move is to start stripping it down and assess for rust and to checkout those rails...
TC.
