360 build advice for my '70 dart swinger

ANTHONY , you strike me as brand spanking new to this. Your asking for the best of both worlds and have a few misconceptions going on.

Lets start at the top.

An excellent starting point to a powerful 360 (IMO) would be the KB 107 piston that will put you at or near a zero deck height. If at a zero deck height, the compresion ratio will be 9.8-1 with ethier head you have. In which I'd go with the "X" head, an RPM or RPM Air-Gap and a 750 carb. Ethier Holley or Carte/Edelbrock and use 2-1/2 exhaust.

The 904 lock up tranny will not show a big, but a very minor gain in mileage which will all be thrown out the window once you start messing around with the engine. The RPM drop is also very very minor. Torque converters for a lock up trans are harder to come by and more expensive with not as many choices unless custom built for more money.

The 276 gears may be great for the Hwy. but will EXTREMELY limit any performance and on top of it all, will absoultely kill any bottom end with even the slightest cam change you make. Move up to 3.55's with the above cam or don't bother.

As far as dual quads go, no one makes a new intake for the engine family. You'll have to find ethier a Edelbrock D66 or a Weiand dualquad intake. The low rise version will fit under the hood.

A pair od 500 Edelbrcoks will work for this intake.
IF a Holley can be bolted on these intakes, a pair of Holley 390cfm sized carb will do great.