1.What do you mean by exhaust termination boxes?

Here is an article by David Vizard on termination boxes or resonator boxes. You can do a goodle search on exhaust termination boxes. Plenty on the subject.
http://www.superchevy.com/technical/...xh/index1.html

2.My primaries are 1 5/8. Do you think it would be worth investing in Don's 1 3/4?

IMHO 1 5/8" headers are to small for a performance 383. I think Don's 1 3/4" headers would be an improvement because they are not only larger but they fit the wider AFR exhaust port better than any header on the market.

 

awesome thanx but id rather stick to maf then go sd...

 

Yes that is Rbob's system. He has been very helpful with my long road of tuning and running into problems. He responds to emails very quickly. I would recommend this setup for the money and support if you ever want to change.

 

Im very interested in the headers. Are you running true duals or his Y pipe?

 

The "Y" pipe but with a 3.5" Mufflex cat-back. Also a 3.5" Magnaflow muffler.

 

Thanks. I will have to contact Don sometime. If you have any undershots of your car, I would be interested in checking your set up out if you don't mind. If not, that is cool either way.

 

It's similar to this but larger pipes/

 

Yes. Thanks Don as I don't have a picture.

 

Looks good. I am running the single cat back with no cat at all because in Oklahoma there is no emissions at all. I am running no smog or anything.

 

and back to FIRST we go...

 

Dyno Don, I am running the Headmen shorties on my car as of right now with 210 AFR heads. From what I can tell, your headers are built to match up to the AFR exhaust port?
Also If I were to install a set of your headers, would my existing Y pipe work or are the lengths different than most other headers?

 

Great informatino here, I'm sold on the FIRST system. It has everything I want. Low end tourqe, fat midrange, and good daily driver set up! awsome!

 

Sorry, I wasn't keeping up with this thread.

No, the connections are totally different.
Each header and y-pipe combination are unique.

I was checking with Ken and he now makes an LT1 setup that uses a stock type throttle body (dual openings).