Draw a full scale cross section of what you have now including the leaf spring to tire distance, wheel lips to tire distance etc and then tape it to a window in your house.

Then draw up a 10" wide rim and tire, also at full scale, and overlay it over the first one you drew and you can easily see if it will fit or not.

If you have access to a cad drawing program this overlay method works great too.

Personally I would rather have an 8" rim with a wider tire and some old school sidewall bulge vs a 10 rim and a smaller tire that looks pinched inward.