I HAVE INSTALLED MANY V6 3RDS WITH NO GRINDING REQUIRED.
THE ONLY PROBLEM I HAVE SEEN WHEN CHANGING TO V6 IS THE DRIVE SHAFT FLANGE. FLANGE IS NOT INTERCHANGEABLE DUE TO PINION SIZE.
THERE ARE MULTIPLE FLANGE BOLT PATTERNS. THIS CAN BE SOLVED BY INSTALLING A NEW FLANGE THAT HAS MULTIPLE PATTERNS DRILLED INTO IT.
HOPE THAT HELPS.