I vote shorty headers. Engine masters did a comparison and I believe shorty headers had an advantage.
Don’t buy flowtech, I thought they made the summit brand as well. Mine had a bad weld at the egr port which cost me extra to have fixed. I bought flowtech because of price and they had the thickest flange.
I had a set of pacesetters which wore out where all the pipes connect to the flange. They lasted over 10 years.
Here’s the flowmaster head pipe with high flow cats and mandrel bends.
Flowmaster 2010023 Direct Fit 2" Inlet/Outlet Catalytic Converter
https://www.amazon.com/dp/B009UODIII/ref=cm_sw_r_cp_api_i_ESjIEb90X76AH
I’ve had luck with the locking header bolts by pro form, they stay tight on my vortec but occasionally need tightened on my 79 k10.
I’ve heard longtubes on carburetor engines to help complete combustion and shortys on fuel injected.
My 79 has longtubes and I messed one up off roading because they hang lower than shortys.