Is/was there ever a 340 Magnum
Probably nothing more than a badge in many cases, IIRC was there was a 440 magnum, that had heads with a larger intake valve, vs the first castings
I'm pretty sure not many people knew about the small increase in the intake valve. ,but the moniker 440 Magnum stuck.
Other actual mods to distinguish themselves 340/440 six pack, Trans Am, exhaust manifolds, camshafts, etc, all factory pieces
It appears for the most part that the Magnum logo presented the engine as "superior" in nature, while not actually being so
Except, referring the info on the past paragraph
so the cool badging was basically no more than eye candy (noting the exceptions)and a way to ramp up sales,