2 1/2" with a H pipe is perfect for a street car. Just add hemi mufflers. This is especially true in a convertible where exhaust "drone" can be an issue.
I suggest a pair of reproduction hemi mufflers. I used them on my 67 Polara convertible with a 2 1/2" tti system. Sounds like day one. Zero resonance, (drone).
Mancini does not include the tailpipe downturns in their quote. In fact they were not aware they were available. TTI includes them. That will offset some of the cost difference. Mancini has disappointed me with misinformation and botched orders enough that I don't even consider them anymore.
Best to contact and purchase from tti. It will be less money and you'll get better customer service. They know what their talking about, Mancini doesn't always ask the right questions and likely will get it wrong.
Also, order the system without mufflers. You can buy them all day long and it will...
While tti lists the same system, 65-73, when comes to purchase time they ask some very specific questions regarding YOM. They are the only definitive suppliers I know of. Worth the extra few dollars IMHO.
whatever your muffler input pipe diameter is, reduce it by 1/4 " for the tailpipe diameter. It will create the needed back pressure to smooth the exhaust pulse's.
tti offers a downturn tail pipe tip that looks great in both 2 1/4" and 2 1/2"
I would also recommend a equalizer between the...
It's hard to beat the sound of a Borla. My 1st choice for a performance muffler.
The resonance issue is more prominent in a convertible. I have used "hemi" mufflers on my last two verts which eliminated the need for resonators.
I think the little extra cost of a tti system is worth it. Comes complete, fits right, high quality, shipped quickly. No back and forth, trying to get it right BS. A clamped system, as it should be. No cheap, short cut welding to rust out. JMHO.
If the valve shaft in the manifold is worn it will leak exhaust like you describe, minor but annoying.
Also, be carefull "resurfacing" your manifolds. I took a set of HP manifolds to a machine shop for truing up and they removed .080 from the right side manifold. It barely fit back on and I...
I swapped to HP manifolds and installed a complete tti system. All fit with little to no effort. (I bought my tti system without their mufflers and installed a set of OEM replacement mufflers). The only real performance gain was going from single to dual exhaust. I don't think the HP manifolds...