Im planning and gathering parts to build a 355 but my 305 has took up smoking and developed a knock i have the 305 from my 87 which was ccq (computer controlled quadrajet) it has a mild cam was told anyway i want to throw a little into before i swap it and my new 700r4 in old one is on last leg. I have a edelbrock Eps 4 barrel intake with tbi adapter. Im gonna look for a good double roller timing chain i have headers going to have my local exhaust shop take my slp's and do a 3 inch back to a y with 1 on each side. Anything anyone can help me on i appreciate.

 

I dont know about your 87 305, but generally heads, cam, exhaust and fueling is where you need to start spending $$$$ to make power.

Fuel pump, VRFPR, EBL flash, heated O2 sensor are the first things that come to my mind that you will need with both 305 and 355 engines.

Flow matched injectors make a big difference too, though depending on the 355 build sheet you may then need bigger ones.

I would simply look for good a single timing chain like Cloyes 9-3157 or the GM performance one, even the LT1 uses that type of chain, they are supposed to be stronger than the double ones.