Interesting project SP!
Some years ago I did some research on this subject. Some single shot riflemen I knew regularly swaged oversized bullets down to fit their odd and obsolete cartridges when moulds were not available. They all concurred that for least deformity and best accuracy, you should try to stage the sizings at .002" each. Sizings greater than that may or may not give satisfactory accuracy.
I gathered up my sizing dies and borrowed all I could and staged some .45-70 bullets (457125) from their nominal diameter of .458" to .445" for a .44 cal. Maynard rifle - and some down to .435" for a 11mm Mauser. They all worked just fine for my needs and rifle-shooting ability.
I eventually got a proper mould for the .44 and could tell no real difference in accuracy between my unsized and sized bullets.
Condition of the bullet base is critical to accuracy - particularly at longer rifle distances. I would try to see if I could swage some with the ram to see if the dimple in the base can be avoided.
Please let me know if you can't find any acceptable 200gr. candidates for swaging to .329".......