Hey Alex, welcome to classicbroncos!
There are no hard and fast rules to this kind of thing. There is no "this is always done" and "this is never done" action in a used vehicle market. About the only thing consistent with them is that some people tell the truth, and some people lie, and still others don't know what they have because they bought it simply to flip for a higher price.
Early Broncos from '66 to '77 were available with only two sizes of V8 engine from the factory (two or three Inline-6 engines over the years, but we're just talking V8 now) and one was the 289 from late '66 to early '69, then the 302 thereafter.
A later model 5.0 liter is still a 302. It's just a newer designation usually to indicate the change over to fuel injection, but Ford was using liter designations long before that. Just not consistently.
The engine in your pics looks extremely original, but that does not mean it's original to the Bronco, nor does it mean that it has not been gone through and refurbished.
But usually if someone goes to the trouble of refurbishing or fully rebuilding an engine, they at least make it look new with some paint and such.
There are no "numbers matching" things with Broncos either You won't find many VIN numbers stamped into various parts. The best you can do is look up the casting date codes and engineering numbers cast into the engine block near the starter and that side of the block. That would at least tell you it was made a couple of months before the Bronco was assembled. That's about as close as you can get to knowing if it's original to the vehicle.
That decal will tell you some things too though, so if it's a '68 Bronco for example, and the number date on the decal is '79, then you can be sure it was swapped in at some point.
Is that your question?
Paul
