A 72 four stroke will swing a 13x6 two-bladed prop. To convert this to a four-bladed prop, subtract one from the diameter and two from the pitch. So you would need a 12x4 four-bladed prop. Here is a conversion chart from Zinger:

http://www.zingerpropeller.com/_2_blade_.htm

There might be some other conversion charts out there.

Here is a comment from O.S. Engines: http://www.osengines.com/faq/product-faq.html#q155

IMHO, I don't think a 72 four stroke will be enough to power your 60" span Mustang. You might fly at scale speed, but you might not have great vertical performance.