I based it off the Flowmaster application guide:
2005 WK 5.7L 50-series PN 9530560
3" offset in / 3" center out

..... figured they didn't change the exhaust system in following years.

Also all ram truck 5.7L applications in our model years have 3" I/O specs.

Guess there's nothing left to do but get out the tape measure! Lol