1/2 to 3/4 of a cup? you'll probably want a mix of lime juice and vinegar. Say, 1/3 cup lime and finish up with vinegar. If you are pressure canning the amount of vinegar isn't so important. If BWB, then vinegar content is more important. Check out some extention service websites and follow their recommended amounts. You can usualy substitute vegetable amounts to suit your taste as long as the overall veg:vinegar/acid ratio remains the same.
Have Fun!
SL