Hi i have recently been wanting to get a 350... for my 87 firebird but my parents dont want me to have that much power. but they have agreed to let me upgrade my car because its currently it is stock, so when i finally can switch to a 350 will i be able to use the parts from my 305 on the 350?

there are sooooo many threads like this, a quick search will get you more info than you could ever want on this topic

but yes, the 305 is identical externally to a 350, induction may need a little tunning/upgrading, carb/TPI/TBI to match the larger engine

oh sorry but thank you

Since your parts are basically identical externally, a good idea is to look more at what you need to replace/ modify in your injection and computer system to get it to run right after the swap.
Basically any 350 made 87 or later will will work (until you get to vortec heads, but even then you can buy a lower intake manifold that will get you back on the right track for about $300.)
Cam, headers, catback, throttle body mods, new sensors(hint hint) will all swap right onto your 350 when ever you get ready.
except your Knock sensor, which is different in a 350 than it is in a 305 i hear.

I swapped a 350 for a 305 in a Caprice and if I remember correctly the only thing that didn't bolt up right was the exhaust manifolds.

That would only be an issue if you had 6-bolt exhaust heads.