i have a 91 sr with a 305 tbi and was thinking about putting a 350 in it. i never built an engine before but i think this might be my first. i am really sure what engine to get i guess i will go to j/y to find one but not sure what kind. what year ,car or truck, any suggestions would help out alot. thanks in advance.

Personally I would look for a 1 piece rear main seal block with the newer style heads if you plan on reusing as much as possible from your 305... I would also try and stick with the tbi setup for drivability and fuel economy( I doubt if gas will ever get any cheaper).
Just curious, for your first rebuild, why not do a real simple low budget rebuild of the 305? It really depends on what your goals are for your car... The last motor I had rebuilt actually came really close in cost to some of the crate motors gm is selling. I started to build a 383 for mine and I have $500 of machine work on the block alone. That's before any parts have been purchased, it adds up really quick. My only other word of caution is I see a couple of guys have threads right now and they are pulling a roughly 200 to 220 hp +/- 305, and swapping in a roughly 200 to 220 hp 350 all while pulling the fuel injection and emissions equipment off, and I have to ask what are they really gaining?

From what I've been reading I would say they're gaining torque. Which even in a mild 350 will FEEL alot more powerful than a 305. Of course, mods can always make a difference.

I stumbled onto a rebuilt 350 last night that a guy I know has had sitting in a crate for many years. He'll sell it(and deliver it) to me for $100. Well, it should be a bunch better than the 305 with 80k plus miles on it that was neglected by the previous owner for 20 years. So even with the same bhp I think I'm gaining alot. Aren't I?

It totally depends on your individual situation... I think guys just get a little caught up in the bigger is better arguement too quickly. Do your research and ask questions to learn as much as you can beforehand. Look around, there are a lot of builds that guys cut up a perfectly good car to swap motors and never complete or get frustrated and give up when trying to get them to run correctly. If I pulled my 305 TPI out of my camaro and swapped in the carbed 350 out of my 1976 camaro I would Lose hp, torque and fuel economy... It depends on the specs of that rebuilt 350, there are some real slugs out there. Just some food for thought. Take it for what it's worth, just my $.02

Smartly said. I agree. My situation is a carbed 305 from '83 with 80k+ miles and I have a couple of gear head friends who know much more than I do about this stuff so they'll be there to put the brakes on the wrong ideas before any money is spent. The 350 has new bearings and rings with only 13k miles on it, supposedly, but we'll get it all figured out and I'll do my best to put useful info on the threads as I learn it.

Yeah, I'm not busting chops, I'm just trying to help a guy not make the same mistakes so many of us have (myself included).

i think i want to do a few cheap things on the 305 while i build a 350 . that way i can still dirve the car while i am building the 350. as for the the bigger engine for me i know i will be the type of always wanting more . i think if i get a 350 i could get more out of it than building a 305 and putting alot of money in it then have to step up later. for me i was thinking of a carb engine because i am not to good with the computer stuff and i think it would be easier for me. the car will be mostly a everyday weekend cruiser with going to the track evey once and a while. not to worried about emmmisions i already took the smog and cat off the car.

If your 305tbi runs good, now is the time to learn the computer and how the fuel injection works. It seems intimidating at first but the more you work with it the easier it gets... A 20 year old car probably needs some tlc anyhow. You might just decide you want to reuse the tbi setup. There is a ton of info and really smart people on here who are always willing to help. There are a lot of mods listed on here you can try, some of them free, you migfht try searching "tbi mods" or different variations of that. I'd read as many build threads and swap threads as you can, there's a lot of good and bad info to help you decide what you want to build. I am also looking to swap motors, that was how I stumble on your thread, I'm trying to build a motor to replace my 305 that actually runs great, but it leaks oil and puffs blue smoke at startup, but it still has tons of power, so I'm trying to come up with a combo that will give me a little bit more power, but not sacrifice fuel economy... I want to keep my tpi setup, I actually love my car as it is, but i can see I'm going to have issues in the years to come. I've been looking into the vortec heads, they are cheap and are supposed to flow well.