A Have A 350/700r4 Combo, With A Holley Street Dominator Manifold, And A Holley 600 Carb On It. It Has Headersm And Its A Daily Driver. What Would It Do To My Performance If I Were To Put A 1" Carb Spacer On It? Would I Get More Torque, Or More Top End Or Both? Would It Affect My Fuel Economy At All??

Spacers are weird Robert...sometimes you'll notice an improvement....sometimes not.
And then you've got to choose between an open, four hole, or contoured (4 to open).
All you can do is try. On a dyno, mine responded best (but only slightly) by using a 1" Super Sucker 4 hole to open.

A Have A 350/700r4 Combo, With A Holley Street Dominator Manifold, And A Holley 600 Carb On It. It Has Headersm And Its A Daily Driver. What Would It Do To My Performance If I Were To Put A 1" Carb Spacer On It? Would I Get More Torque, Or More Top End Or Both? Would It Affect My Fuel Economy At All??
I use a spacer under my current carb but have no dyno sheets or times to prove that it helps.The reason I use a spacer is to isolate the carb from manifold heat in hot ambient temps.I chose phenolic and the carb temp is noticibly cooler than previous.If you do not want to lift the carb and increase plenum depth....1/2 inch phenolics are available.Your daily driver may like the phenolic removed though if you drive the car in the colder months.

When I dyno'd my engine, I did not see any significant gains with a spacer. We tried upen, 4 hole, 1/2 and 1". The only difference I saw was when we changed to a HOlley HP 750 carb and the Super Sucker. I saw a 5.2hp gain for both. Wasn't a big deal for me.