have a 92 5-spd LB9 305 TPI w/5-spd....
wondering what i need to do to have a smog legal swap to a 350...
how bout ECM?
would the trans affect the ECM? I was also thinking about a borg warner T56 six speed swap cuz i know the T5's can't take too much abuse

 

It'll stay legal .. IF YOU change the CHIP (not the entire ECM.. you only need to replace the chip).. you will also need to look into 350 Injectors/pressure regulator. and the only other thing is make sure the EGR valve is designed for a 350 .. other than that It'll work
Since you are already going to need a new chip for the ECM.. tranny doesn't matter.. when you get a chip .. you have the option to get is custom.. they ask engine size/intake/ cam/exhaust/TRANNY type.. you will have SOME trouble switching from a 5 speed to a T-56.. .. it'll bolt up just fine... BUT you will need to replace the hydrolic clutch cylinder and plumbing.. and it weighs about 2x the weight of a 5-speed.. so a NEW and probably custom transmission mount.. you will also need to RE-CUT the console for the new shifter lever.. It's a few inches farther back than that of a 5-speed
they are a pretty penny however (about $2000 new..) YOU WILL NEED TO USE A T-56 BELL HOUSING AND CLUTCH ... it WONT fit the 5-speed one
GOOD LUCK

 

Technically, it can't be done, since GM didn't offer a 350/5-speed passenger car option in '92-later versions.

For all practical purposes, you could get a 350 long-block, pull the 305 and swap everything over to the 350, and put it back together. It will run and run cleanly enough to pass the sniffer. And, it will look just like a '92 305 (as long as you have center-bolt valve covers on the 350). IF they ask you what engine you've got, tell them to read the stickers.

In order to get it to run well, you'll have to do the PROM- and injector/regulator-thing above (an adjustable fuel pressure regulator, which can be made following the recommendations in the tech article on this board, is a much better idea than a 350 regulator). PROM tuning makes more sense than a different pre-programmed chip, though.