67 burban question

[67Sloburban]

i have recently got a 67 suburban c20 the problem is i havent worked on a classic vehicle in a long time. the PO said he only had it 2 years and it just sat in his yard but as far as he knew it was all OE. i know for a fact it has 68 or 69 front fenders on by the side markers, it has a 283 sb in it but im pretty sure its not the original by the 4 barrel carb and HEI dist but can i tell what it from without pullin the motor. i apologize for the noob question but im just tryin to get back to my root since my family all had muscle cars, but any help would be appreciated thanks