They are both internally balanced, so it should work fine.
yes the heads will bolt right on but if you are putting a 305 in there the flywheel is different in the sense that the 327 has a small hole where the flywheel meets the crank (you need the starter for the 305)
The Chevrolet small block 400 will bolt in place of the 305 but be sure to use a 400 flywheel or flex plate. Do not use the 305 flywheel or flex plate on the 400.
A small flywheel needs to stay with the starter that goes to it. You can use either flywheel, and the block should be drilled for either starter.
The 305 shares stroke dimensions with the 350, so if you put a 327 crank in a 305, you'd have a de-stroked 305 with almost no compression. Displacement would be around 287 cid.
FLYWHEEL
yes
Yes, it is same flywheel.
no
yes
the timing mark is an engraved line on the flywheel. there should be a metal flap offset of the flywheel with markings for A (advanced), O (ontime), and R (retarded). use a timing light connected to the spark plug wire for #1 cylinder. That is how it is in my 65 impala 327 Minor correction is that the timing mark is on the front damper not the flywheel.
No. You would need to bore the block to 4 inches, which is too much for a 305.
Depends. There were 168 and 153 teeth. Both were used on 305's.