You guys are over thinking this, and ALL of California does not require as strict of smog laws. (my uncle lives in a county an hour and a half away where they dont even smog, right in the middle of California)
Ive got a 77 that I have smogged at different places in my LOCAL area every year and it has passed with flying colors. Only one year did I have an issue and that was because I installed an open air filter element but had the stock one with "stove pipe" that comes off the headers in the garage. Not one time did they check for any kind of engine stamping or VIN. My engine is either the 260 or 290 crate engine.
OP, go to where you plan to have the truck smogged and ASK THEM what is required. HOPEFULLY they will look in their book and not just their computer and see what the application requires for your truck SPECIFICALLY. For example, my truck is the "Heavy Half Ton" and DOES NOT require a catalytic converter. I've literally got exhaust straight off the collector to a glass pack to the tail pipe. Each time it has thrown off the smogger until he checks the book.
Id get the 290hp crate engine if I was you. The application in Summits online shopping does NOT always match to what is correct. I've returned 3-4 things this year because of it.
If you have any other questions or need pictures, shoot me a PM. Id be more than happy to help.
Like 78trk said, get this one,
http://www.summitracing.com/parts/na...make/chevrolet