Welcome to CHR!

All of the accessories will bolt up from the 305 to the 350, AC, alternator, power steering pump, water pump, pulleys, etc. I'd invest in a new water pump simply because the one on the 305 is 31 years old. The alternator may be a good one to swap out as well as new belts and hoses.

Carefully clean and label everything as you disassemble - take lots of pictures and write everything down. Make sure you disconnect the battery and remove it before you begin removing the accessories as a quick short to ground can make a real mess of wiring that's a pain to replace.

You'll need a different manifold for the 350 - not due to size - but to go back to a carburetor. I'd recommend a Weiand spreadbore manifold and a fairly stock 750 Quadrajet (Summit Racing is a good source).

I'm assuming you have access to a garage, an engine hoist (you can rent one as well) and a good engine stand.

Assemble all your parts, ask us lots of questions and you'll be just fine.

Let us know how you decide,
Glenn