Complete rebuild 454 ??

[Rnd]

1977 GMC C2500, 2wd, 3+3, 4.11 rear, 700r4 trans.

I replaced the 400 THM with a rebuilt 700r4. Now it's time to refresh the engine.

I started out at about 12 (11.7) mpg before trans replacement I'm now around 15 mpg.

When traveling at highway speeds 70 mph+/- it has very little to no power/torque to climb hills etc.. With the overdrive and lock up I've taken the engine out of it's power band. For those that remember. The 70's were not good years for the automotive industry....Oil embargo, emissions, federal speed limit of 55mph, unleaded fuel, and limited technology did not add up to very good performance....

So my question/questions...I have a stock 454 mark 4 with 71,000 miles. (Numbers matching stock engine.) I'm going to do a complete rebuild but don't know what components to use????

Looking to increase low end torque yet preserve fuel mileage.

Primarily I would like help on piston and camshaft recommendations.

Also I could use some help on what cylinder heads I may have. (round ports or oval) and what is the difference?? I really don't want to buy new heads. That would kill the rebuild and send me into crate motor territory.

Offer up some ideas,,,, Please.

P.S. Would like to hear from the guys that have done a few and know the pit falls.

Thanking you in advance, Randy