I have a 2004 mustang that has a 3.9 ltr v6 that blew a rod I'm attempting to swap in a 3.8 v6 that was casted by the codes on the block in 97. What major things am I gonna have to do to complete the swap such as swapping heads? Buying a fly wheel with a counter balance as the 3.8 has a counter balance on the front pulley and my 04 3.9 does not. Any help is appreciated. Thank you!