The stock vortec heads have a limiting exhaust port configuration. This why ANY non-stock Vortec head will give you gains, just how big of gains depends on what heads you use. You can spend thousands on boltons, I wish I would have just gotten a set of head and a cam from the beginning. The stroker was out of my budget, but is a nice addition.
Longtube headers from Hooker pn 2462 with 1 5/8 primaries an 2 1/2" collectors will fit your truck and will allow you to eliminate the not so high flow stock headpipes(pipes from manifolds to cats) which measure 1 7/8's OD. These headers are available in stainless 2462 2HKR, steel ceramic coated 2462 1HKR and painted steel 2462 HKR, prices are $570, $324 and $180 respectivley.
I used aftermarket dual 2 1/2" cats connected to the headers via dual 2 1/2" stainless headpipes. Headers, exhaust and a PCm tune dropped my 1/4 mile times by 3/4 of second and the truck drove completly different, very very nice improvement. And this was with a completely stock L31 Vortec 350 just like yours.
I welded in some O2 sensor bungs in each headpipe, so i didnt disturb the ceramic coating. If you wish to retain EGR then you will need to add an EGR supply fitting to the drives side header, any competent exhaust shop can do this for you.
If you ever plan on forced induction in the future, I suggest you step up to the 1 3/4" primary 3" collector Hooker Super Competition header p/n http://store.summitracing.com/defaul...=egnsearch.asp
these HOK 2806 1HKR are ceramic coated for $728 and the HOK 2806 HKR which are painted steel for $419US.
If you are building a stroker, you may want to consider offset grinding the rod journals to the small rod size which will net you a stroke of 3.875" and with an overbore of 0.040 or 0.060"(cant remember) will rsult in a smallblock 396 cubic inch engine. Nice ring to it IMO.
Just an idea to be a bit different.
The Fastburn heads have 210 cc intake ports and have D shaped exhaust ports, large tube headers are required to cover the exhaust ports properly. For this reason I would probably gp with the large port BOWTIE Vortec heads as they have a more conventional exhaust design. The Fastburn heads use the LT1/LT4 exhaust port design. Hedman makes a D-shaped port header, not sure if they are made for the trucks though.
Let me know what kind of emmissions testing you have in your area and a max. money budget, what you use teh Tahoe for and what you expect and then we can help you pick a package much better. When I do this for poeple, I feel like a kid in a candy store.
Ohh, that spacer you are talking about. Since the injectors, fuel pressure regulator, injector wiring, supply hoses and all the other injection crap is on the INSIDE of the intake, I can see that spacer helping airflow inside of the plenums. They make some bold statements about flow increases, I think gains are probable, to what extent I dont know. The money you put into that intake spacer, will only leave you about $500 or so left on a Marine Intake. I got mine from a friend in the US for $750 US complete with injectors that were flow tested. If you want I can put you in contact with him. He sells a complete package that includes colour coded wires to match the stock truck injector loom wires, injector plug connectors. He also sent me 2 t-body gaskets for the 454 and 496 bigblocks as the Vortec 350 uses a sela in the intake, but teh marine intake doesnt have this seal, so the bigblock throttle body gaskets fit 100%.The only thing I needed was to buy some fuel line hose and fittings along with intake manifold gaskets. I did the whole swap, including shipping on an 80 lb package from teh US, plus border charges for under $1000 US total. The MArine Intake parts if you bought them new would be over $3000US. Going used is the way to go. I saw a marine intake go for $900 on ebay.
I was the 2nd person of our Marine Intake project in North America to install the intake. I am using the stock Marine injectors which flow 28 lb/hr at my 60 psi of fuel pressure. I have noticed much better higher rpm power, I am running a stock longblock with boltons and headers.
Here is a thread all about the Marine intake conversion. A Ramjet intake manifold can slo be used and on a NA engine will probably be worth a few hp over the Marine piece. The intek runners of teh MArine intake are slightly larger than the stock L31 truck intake. The MArine intake was used on Marine 350 and 383 engines with ratings up to 330 hp.
Here is another pic of the Marine intake
I am using teh L31 stock truck T-body and the nly tuning change I HAD to make was to change the injector flow rating. Obviuosly more power can be made when a proper dyno tune is done. But its not like the truck wont run without tuning.
You already have a 75mm throttlebody, I suggest taking your stock t-body and removing the EGR diffuser plate that looks like a 1/2 moon shaped piece on the back of the throttle body. I would only use a larger throttle body with a supercharger. The 75 mm piece will for sure feed a 383 just fine. I think yiou could even use a 78 mm LS1 t-body, but the increase in T-body size is not worth the tuning headaches, unless you plan on getting a dyno tune.
Post back with any questions, we'll try to get them answered.
Sorry about the book, I love Vortec stuff.