Name some? Prefer stock/quiet style and prefer the inlets to be fairly close together.

 

My flowmaster muffler is the exact opposite, single in, dual out (to create dual exhaust) Its a 50 series, which is quiet on idle / cruising but is loud when your foot gets heavy

Flowmaster 50 SERIES HD HEAVY DUTY MUFFLER

 

There are lots of brands. Even flowmaster (but they are directional)
Dynomax and magnaflow are reversable (straight through) and not as quiet as you probably want.
You should be able to find a real muffler like you want. I usually go on ebay and look things up.

 

What size are your headpipes?
How much do you want to spend?

The Bear River 22" WickedFlow is stainless, pretty quiet and reversible due to it's design.
It is perforated, not louvered like some other brands.
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I used a giant school bus muffler from the Walker heavy duty catalog with 2 1/2" inlets and a 3" stainless universal Magnaflow tailpipe.
http://www.walkerheavyduty.com/catal..._InletSize.pdf
You can see all the dimensions here.

This 22822 muffler is really heavy gauge and the internal volume is immense -so the tone is deep and mellow- but it has no packing to wear out or hold moisture.
All I had to do was weld flanges on the inlets and make a new rear hanger.

 

My want to spend versus what I likely have to spend is different... I wanna keep cost low.

EFI manifolds into true dual stock sized pipe. I want to merge it into one and quietly.

 

I'd say weld yourself a y pipe and get a normal muffler.
It's tough to find a dual inlet real muffler other than oem.
Walker looked like they had a great selection to look through though.

 

For the I-6?
Just get the big Walker Y-pipe and a single in-out muffler.
You'll be time and money ahead.

 

I guess to be specific, I swapped a EFI 300 in my Bronco with F150 harness and will the Walker I can find for a F150 fit the Bronco?

 

I think the frame (in the front) is the same 150->Bronco.
Just the back half where the body and tank mount differs.

If you get the 45166 pipe take a 1 7/8" hole saw and cut out the excess blocking the short side. Go 2 1/2" from there.

 

Yeah, the pipes that were on the motor, on my 91 F150 all bolted up fine, just a little too long at the rear tire. Had to cut it off there. My Bronco thinks its an F150 anyhow.

I seen some other straight six Bronco guys that put that pipe on fine and about the bottleneck. Preciate the info, it prolly will be cheaper to just buy the pipe.