To simplify the expression \( \frac{7^3}{25^{-4}} \) using the property of negative integer exponents, we apply the rule that states \( a^{-n} = \frac{1}{a^n} \).
This means that \( 25^{-4} \) can be rewritten as \( \frac{1}{25^4} \). Thus, the expression becomes:
\[ \frac{7^3}{25^{-4}} = 7^3 \cdot 25^{4} \]
Now, let's evaluate the options provided:
- \( \frac{25^4}{73^} \) - This option contains an error in notation (73^).
- \( \frac{7^3}{25^4} \) - This is not equivalent, as we need to deal with the negative exponent.
- \( \frac{25^4}{7^{-3}} \) - This is not equivalent, as we also have the negative exponent issue.
- \( 7^3 \cdot 25^4 \) - This is the correct expression we derived.
Thus, the equivalent expression with only positive exponents is:
\[ \boxed{7^3 \cdot 25^4} \]