yes
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.
yes
lt1 has about 295 stock at flywheel, ls1 has about 305
Yes, but it will need to be rebalanced first.
FLYWHEEL
Depends on what the 305 is in, a 305 camaro engine needs like a 9 tooth starter because the fly wheel is 12.75 inches in diameter with 50 some teeth. A 305 in a Chevy half ton will have like a ten tooth starter for the 14.25 inch diameter flywheel that has like 60 some teeth. All 305 engines before 1986 are the same they did have different flywheels for what ever Chevy put them in. 1986 and newer 305's had different cranks the flywheel bolts up different on a 1986 305 compared to a 1983 305.
yes
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.
no
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)
no
yes