Looks like you have done this once or twice!
The only thing extra will have to do is mill the head because it is aluminum and they do tend to warp when removed.
I,ve just completed a head gasket on my car and they removed .005' just to clean it up.
It looks like I found a used engine with 340-390lbs compression. It's a 603.960 engine but I think it can be used in the 300 sdl.