There are a few smog legal swaps out there but not many. I’m not too far from you and am still gathering parts for a 5.3/4l80e swap in to my ’89 K5. I haven’t gone through the actual referee process yet but here’s a short list of things to look out for that I’ve learned from other CA swaps on various forums:
-All the smog equipment must be carried over from the donor vehicle. Cats, O2 sensors, and evap system. The evap system is what screws up a lot of people but it really isn’t too bad/too much extra work if you know about it up front. Basically you can mount the canister and canister vent solenoid near your tank and install the FPS (fuel pressure sensor) with an in-line tee along one of the evap lines. The tricky part is that the PCM also needs to see the fuel level so it knows when to purge or not. I’ve seen a couple of guys just try to bypass that with HP Tuners but then get caught and failed by the smog ref. One way to cover both of those is to adapt and install a late model sending unit in to your tank since they’ll show your PCM the fuel level and also have the FPS built in to it.
-For bolt-on performance mods you’re basically SOL with most of the common stuff since you’re limited to whatever is CARB certified for your donor vehicle. No long tube headers allowed and most of the approved shorty headers gain little to nothing over the newer OEM manifolds so they aren’t worth the extra $$$ IMO. Most of the big name cold air intake companies all make CARB approved products so lots of options there.
-For internal performance mods as long as you stay mild there are lots of options out there. The main trick is to make sure it still looks and sounds like stock as in no super lopey cams or aftermarket heads with brand names stamped all over. Switching to the TBSS/NNBS intake is another really good bang for your buck mod. They flow a lot better than the ’99-’07 intakes and you can usually pick them up complete with bigger injectors and throttle body for a couple hundred bucks or less. Really, if you want to go through all that you might as well just start with a Gen IV 5.3 since it’ll come with higher compression (9.9:1 vs 9.5:1), better flowing heads with bigger valves (799/243 vs 706/862), bigger injectors, and better flowing intake.
-For camshafts I would avoid the Z06 cam in a 5.3 since it shifts the power band too far up in the smaller displacement engines for most people's preference (lots of happy 6.0 guys though). Brian Tooley, Cam Motion, and a few others all have drop-in cam shafts specifically made for the truck engines and most cam shaft companies will even make a custom grind specific to your application for little or no extra cost. How far you want to go with CNC'd heads, cams, valve springs, etc just depends on your budget.
-The E-Rod engines and packages are nice and convenient but not really worth the super high cost IMO. Just the 5.3 (LC9) e-rod package runs $7-8k and that’s without a trans… You should be able to get a complete take-out engine and trans for $1500-3000 (maybe more) depending on engine size, year, and mileage.
Good luck with your swap. Keep us posted once you get going on it
