X-2! The TTI system I bought for my '72 Valiant/360 Magnum was a joy to install becauseEVERYTHING FIT, and made installation a snap.
I am a lousy mechanic, on top of being older than dirt, and I had no trouble at all.
There's more to a set of headers than just how much HP they make, although on a mild engine, the TTI's seem to do very well in that respect.
My low-boost (10-psi,) Vortech-supercharged 360 has a stock short block (except for the Hughes cam, which is very mild at 114/118-degrees @ .050"-lift,) made 445 rwhp through these headers, so I don't think they are too restrictive. (Stock OEM heads, too.)