I had a '74 CR250 elsinore that had the frame mod to steepen the steering angle and a reed valve, DG pipe, 38 mikuni, Works Performance shocks, all new '76 model gears etc. It was as good as anything out there but a lot of work went into it.
13.5 shocks are too short, std is 14.25, you will only make the steering slower.
I wouldn't mess around with any MT parts, those bikes weren't much good and the cases have the oil pump in them. CR bits are plentifull in the US