"I think your question is will the heat gradient caused by the incoming fluid extend down to the outlet and affect the cooling potential of the the fluid leaving through the outlet"(wrcbonk).
That isn't what i had in mind, but that may be another problem.
Yes many people that are doing RB swaps are using a radiator that has the in/out on the same side. Almost all of them are whats know as a double bypass radiator.
Here's how they work.
As you can see there is a plate in the end tank thus blocking the path of least resistance. If the plate wasn't there the coolant would completely pass the radiator core. Instead it would stay in the end tank, and flow out the outlet. As you can imagine that wouldn't do much good. However this has nothing to do with the topic on hand. As the flow on a double bypass radiator is from side to side and not top to bottom, like the radiator you have is.
What i originally was trying to say was that by moving the inlet over a little bit you are changing the path of least resistance. Which means that the coolant might not pass through the entire core of the radiator. Therefore it isn't being used most efficiently.
Tony D if you could chime in on this that would be great!