The slat design on the current wing is accurate for the 737-100 and 200 but not for the 300.  At the end of the slat there should be a small section of the wing that is not part of the slat, much like what you see on the 737NG.

I have attached a few pictures of the real plane as well as a render of a 737 wing I have made in 3dsmax to explain the detail.

Real Aircraft:
https://ibb.co/BT86SZp

What the end of the slat should look like: