Yes it will.
yes
Yes, but the exhaust Y pipe from the 305 may not fit the 350.
yes
The connector into the intake manifold of a GM 305 and 350 has been known to be quite fragile. If the connector has broken you have little choice but to replace the manifold.
A 5.76 car exhaust manifold will fit a 1997 350 Vortec. Your local auto parts store or car dealership will be able to give you a detailed list of all car exhaust manifolds that will fit.
$300-$350 depending on the shop.
yes, direct bolt-in. Might be necessary to transfer peripherals from the original engine such as intake manifold, exhaust manifolds, ignition system, front pulleys, oil pan.
Exhaust manifold torque is 25 lb/ft with anti-seize lube.
The only one I can think of is the exhaust Y-pipe may not fit from the 305 to the 350.
305s had 1.72" intakes with 1.50" exhaust valves. Depending on the 350, it could be the same, or have either 1.94" intake and 1.50" exhaust, or 2.02" intake with 1.60" exhaust.
Well I have the reverse, 454 manifolds on a 350, so I would think so.