should be? really?
Robert is probably right about the additional varnish and gunk.
If so, that is important to clean up. That's the heavy end of fuel, not specifically the ethanol, but it is worse in today's street fuel than was before reformulation.

But to tune a non-stock carb you need to understand it better. So go back to my post above for what you should do next. As mentioned it's also very important to get the timing correct. Then its easier to get the correct throttle position and idle rpm. Once the throttle position is correct the mixture screws can be used to fine tune the idle mix.

Frankly, I find it hard to believe a '70 up 440 factory timing curve started with 30 degrees. But show me wrong, then I'll believe you've got a good baseline to start tweaking. Your engine is stock, so factory is a good starting baseline.

Maybe this will help:
Initial timing (aka Base Timing). Usually set at an rpm below the rpm where the mechanical advance begins.
Mechanical advance: The timing added. Maximum mechanical advance is built into the distributor. For example a slot plate stamped 11 (distributor degrees) will allow roughly 22 degrees.
Total Timing: Almost always refers to Initial+maximum Mechanical Advance.
However, the factory engineers were sometimes more clever than hot rodders and racers appreciated. Some distributors have a very heavy secondary spring so the weights don't hit the end of the slot until 5000 rpm or higher. So, just pick a reasonably high rpm, like 2800 or 3000 rpm and just be consistant in using it for the "total timing".
example: Set the initial timing at 600 rpm to 10 degrees BTDC. Using a distributor with a 22 degree advance, expect Total to be 10+22 = 32 degrees. The rpm it will hit 32* or even 30* will depend on the springs.

Vacuum advance: Usually not used when setting initial. On an original engine, you'll find some use manifold source and others a timed (aka ported) source depending on year and engine. The ported vacuum is sourced so it provides zero vacuum at idle. Otherwise it is the same as manifold vacuum.