Is it 305 or 350 How do you tell

First time mechanicing project. 86 Iroc t-tops...got a body and a tranny nothing else......got to start somewhere....anyways first I thought I would start by learning ...figured it was a good place....first question is how do you tell what kind of engine is in a vehicle by looking at it....If i go junk yard hopping how will I know if I am looking at a 305, a 307 or a 350? And is there any good publications or sites that will help me solve this and other identification problems such as what kind of tranny...rear ends....what not....Hey I warned you I was new at this...Hopefully I will learn a lot and have a good time with this project....

If your lucky the engine data or emissions tag is still on the underside of the hood, or infront of the radiator or sometimes on the strut tower it will list the engine size in liters and the production code of the the motor and emissions and tune up data. Sometimes your lucky and the motor the car or truck is sapose to have is still in it, I bought a 350 before sight unseen from a 3/4 truck should have been a 4 bolt 350 and ended up been a 305 car motor, so it can happen that they have been switched. For more info you can get the 5th digit of the vin on 66-80 cars and light trucks or the 8th 80 and up. I would consult a gm code book for positive id on the block codes and such sometimes too they will give you the order codes of an item listed on the vehicles built sheet as for the the trans and dif id and gear ratio can be helpful in finding the good parts...good luck to you in your seach just be careful just cuz the vin or data sheet says it has something doesn't mean it does also fyi most 86 and up chev 305s have 5.0 LG4 on the back of the block next to the oil pressure switch or sender.

I'd pick up anything with a 4 barrel carburetor that looks stock. I don't think GM put a 4 barrel on a 305 or 307. Otherwise, the casting number on the back of the block will tell you. It's drivers side on the top where the transmission bolts up.

Well, I went back and looked at your post and you're looking for a 1986 or newer engine? That makes things a little more difficult. Get a list of 350 casting numbers and get an engine that matches.

Here are some numbers to look for:
10051184 350 86-up Car & Truck 2 & 4-bolt Passenger stick 1-piece seal
10054727 350 86-up 155-205 Car & Truck 2-bolt Passenger stick 1-piece seal
10066036 350 86-up 205 Car & Truck 2 & 4-bolt Passenger stick 1-piece seal
14011148 350 87-89 2 & 4-Bolt Roller cam one piece seal
14079287 350 86-90 2-bolt Passenger stick one piece seal
14088526 350 87-89 2-bolt Roller cam Passenger stick 1-piece seal
14088548 350 86-88 155-195 2-bolt Truck Passenger stick 1-piece seal
14093638 350 87-95 155-255 Car & Truck 2 & 4-bolt Passenger stick 1-piece seal
14101148 350 86-up 2 & 4-Bolt Passenger stick 1-Piece seal Roller cam
14316379 350 68-88 155-255 Car & Truck 2-bolt Passenger stick 1-piece seal

thank you all very much for your info.....I guess sometimes you will have to hope for the best if you are going to junk yard it.....thanks again...my quest for knowledge continues.....next week new question....later..