714 wasn't a magnum head/ it was the last of the LA series engine heads in 91. 714s are the same thing as 302 heads.
Yeah I know what you mean though about gas mileage. My 01 Durango w/a 360, is no picnic there, gets an overall average of about 12.5, in combination driving. Sometimes can coax 13 out of it as an average. Lower in cold weather and if most of the miles are from my wife driving to work and back, lots of 30mph and too damn many stop lights
but it just passed 300k miles a few days ago.
Still cheaper to drive than buying something else for improvement in mileage and adding a payment and (because of the payment) mandatory full coverage.