"Right" and "Left" bank is usually considered from the perspective of the driver's seat. It get's less clear when the engine is mounted transversely... front and back are obvious, but "left" would refer to the bank that would be on the driver's left IF the engine were installed longitudinally. Cadillac Northstar, for instance.
Frankly, if you don't want to buy new, just measure and mic everything to see if there is anything out of spec. I don't think those parts have any "handedness", and keep in mind you'll have to adjust valve clearance anyway. It's very likely all the intake and exhaust pushrods and rockers and lifters are identical - with the possible exception of wear.
Buy new. 351C/400 parts are dirt cheap. You can probably get an entire valvetrain kit from a place like Summit or Jegs, and maybe avail yourself the opportunity to buy new performance cams suitable for your purpose as well.
To answer your actual question: I have no idea. Even if I knew, how would you identify which rockers are paired with which pushrods? How can you be sure the whoever removed the parts followed the convention?
If it was me, and I knew I was going to reuse the components and cared, I would have put each set in a ziplock bag and labeled them by cylinder number. I doubt I would be that concerned, since there's no way I would put the engine back together without checking and adjusting valve clearance. I realize this is little help to you now.