340 4 barrel and 340 6 barrel: were they really UNDERrated?

Most '68 - '71 A bodies ran mid to low 14s bone stock. A low option car, 4 spd, 391 at sea level altitude good driver all the stars aligned maybe a tail wind can dip into the 13s. If someone ran low 13s stock 340 A Body that is highly unusual and ppl will struggle to believe it. Not saying not true but that not generally how they ran. Stock 2 1/4 crush bent choke exhaust, 1 5/8 inner diameter chrome exhaust tips, giant pinch in head pipe for torsion bar. Stock had less then ideal carb jetting and dist curve. Valve in pass exhaust manifold causing excessive heat in intake manifold ect ect ect..