2. It uses an ~11:1 compression ratio, so forget about slapping on a supercharger or turbocharger without going through the bottom end and replacing pistons. Might as well plan on buying new rods, too- this engine uses the same frail rods the new cars are known for.
This engine certainly isn't going to respond to bolt-on mods like the old pushrod 5.0 'cause it's already near its full potential in N/A form, and as you rightly said it's unlikely that you'll be able to stroke it out for more displacement either.
The only easy route to more power would be to swap in forged pistons/rods and lower the CR to allow forced induction. The stock hypereutectic pistons have thin ring lands that'll break if there's detonation, and I wouldn't gamble on taking the stock powdered metal rods above 7000rpm or subjecting them to the higher cylinder pressures from a blower.