I have bought 3 sets of shorties from eBay over the last 15 years or so and I'm pleased with them: stainless steel, thick 3/8 flanges at the engine, no need for the faulty graphite gaskets and janky stud & springbolt at the y-pipe.
As
@Eric the Awful stated, they
are a compromise, but as a bolt-in, they're better than the restrictive manifolds. Seeing as I've installed them on daily drivers that doesn't see over 4500 rpms, (actually it's rare for me to run it over 4k) they're very cost effective. Where longtubes shine is 4000-7000 and the TBI is well, not a screamer? Hell, my Vortec 5.7 orange zones at 5k...
As per emissions (for those in States that require emissions), they leave the O2 sensor and catalyst in the stock location. Though now that they're more than 25 years old, mine might not have the converter anymore.
Anyway, I happen have a new unused set for a V8 TBI, but since you haven't stated what vehicle you're planning to modify, I'll wait to offer them to you for the $106 that I paid, (plus shipping to you)