Well there was your swap... you sacrificed gas mileage for power. Easy choice id say.

 

Well i guess if 4mpg will break you , might wanna stop now!!

 

im going 331 purely based on the rod/stroke ratio.

nothing to do with reliability issues with the 347 (theyre long gone, and a lot of 347's use a 331 piston on a 5.315 rod).

just in case the engine "has" to see 7000rpm once in a while...