Extra hp out of my 340.

OP--Your engine sounds like its a pretty good performer as it is. As other have said headers will help a good amount. Start there. If it were mine I'd be looking at a nice little solid cam next, since the 340 is known for being a revver and all. Then when the oil gets hot from your highway jaunt with 3.73's the valvetrain will still be in control and making the same power as before. A properly spec'd solid will pick up the bottom end torque a bit and carry power upstairs that a hydraulic cam could only dream about. Use the 340 as it was intended-for RPM and HP. Don't try and make the 340 into something it will never be. J.Rob