A 200 six cylinder is a straight six, and as far as I can recall, it uses the same belhousing as a small block V8.
The V6 engines have a different bellhousing.
Have you already tried to mate the convertor to a V8 flexplate??
If Im not mistaken (which is a possibility!!), the 6 cylinder convertor may have its mounting bolt pattern in a smaller diameter than a V8 style, so it would only be a matter of drilling the extra holes in the V8 flexplate.
The V8 bellhousing and block plate will work as is.