The best way to identify the engine is to get the numbers off the block and look them up. Goto this link http://www.nastyz28.com/sbchevy/sblock.php and it will have all of the block casting numbers on it.

You said that the motor is an 80s 350 out of a truck? If you can't get the casting numbers for some reason goto the scrap yard and look at an early 80s and late 80s chevy pickup with a 350 in it and visually compare the pulleys to eachother. One of the two will fit just fine. You can even get a pulley off of a caprice or any other V8 chevy car from that timeframe. The great things about old chevys is that almost everything is interchangable between models.

Hope this helps some. Any questions just ask