whats the best engine for both performance and mileage??

Sorry.As for the 4.7,I have 1 or 2 calls a month,for reman engines.The thing that scares me,no rebuildable cores.As a parts person,that is bad news to me.Hot Rod dyno tested a stock Magnum 300/360.Made 315 h.p.,400ft-lbs of torque.Torque,makes it fun and punchy down low,dies off around 4800-5000.Torque in that area,makes it efficent for m.p.g.It was carb,dual plane intake.Too big a header.Hopefully,this helps.