I ordered a new 58mm TB from summit. Took some pics:

 

If you attempt to run straight back from the TB mounting surface at 58mm diameter, you'll break through the casting on the passenger side so be careful over there.

 

Did you learn this from experience? If so, tell me you have a pic. for the heads up.

 

I didnt bore the holes, but I told them to just drill away and I'll fix it later. Had the plenum welded up on that side and smoothed it out on the inside. I also had to alter the runner to clear the weld.
I have pictures somewhere.
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https://www.thirdgen.org/forums/tpi/...hat-i-had.html

 

Thanks for the info. I plan on building a 383 stroker in the future, but for now, all my $ is going to my '54 Chevy truck project with a very mild 350. Will I need to do any tuning to the ECM in order to run the 58mm TB and AZ. S&M runners with the stock base and port matched plenum? When I get to the 383 I'll get a better flowing base intake, but for now the IROC is a daily driver. I do realize that the 58mm is overkill for the stock L98 with stock heads, but I only wanted to buy the parts I needed once. My polished intake/runners/TB on my IROC will be going on the '54. I got the AZ. runners and 58mm TB for the satin look. See the '54 project link in my sig.

 

I had both sides welded up when I modified my plenum to 58mm like you did. When they are blended in it looks factory.

 

I just got off the phone with Ben at AZ. S&M and they have no record of my order last week So now I'm 3 weeks out on my runners I'll update this when the port matching is done.

 

3 weeks? There are people on an AS&M runner group purchase on this board that have been waiting since September. You've got a long wait.

 

I paid $435. How much would I have saved with the GP?

 

I'm in the GP. IIRC I paid $362 shipped. It's been a long time.

 

Are they made by AZ. S&M or does someone else produce them? Are TPIS' comparable?

 

TPiS and AS&M runners are identical. TPiS bought the plans from AS&M and then mark'em up.
They are separate companies that make the same thing just under different brand names.

 

Thanks Viper killer.