Camshaft manufacturers have to be able to give the consumer some idea of what to expect from a particular grind, since most of us don't have the experience with testing different camshafts to know how our engines will respond. Of course, since our engines are not all the same, the behavior after the addition of an aftermarket performance cam is still often a relative unknown. In addition, since engines like your Oldsmobile were offered in such a wide range of displacements, blanket statements regarding the operating characteristics of a given camshaft have to be somewhat vague. It should be pointed out that the fine print in many camshaft catalogs details the engine that was used to determine the operating characteristics; in other instances, idle quality and rpm range are broken down into displacement ranges.
Your question indicates that you are aware of the effect of displacement on operating characteristics-the general rule is, the bigger the engine, the "smaller" the cam will seem. This is simply because the larger the displacement of the engine, the more air it moves for each stroke, and by moving more air, the larger engine is better able to dilute the effects of the camshaft's overlap, which is the aspect of cam timing that most affects idle quality.
The factors that cause a bigger engine to idle more smoothly with a given performance cam actually affect engine performance for the entire rpm curve. Using your example of the 260 and the 455, for comparison's sake, let's say they have the same cylinder heads and compression ratio, and the same cam is installed in both. Since the airway and the valves and valve timing controlling that airway are constant, potential airflow is the same in both engines-only the displacement is a variable. So, to utilize the same amount of airflow, the smaller engine has to rev higher, since it moves less air with each individual stroke. This means the smaller engine will make its peak power at a higher rpm than the bigger engine. A cam that seems "big" in the small engine, one that makes it idle rough and allows it to make peak power at nearly 6,000 rpm, would probably idle relatively smoothly in the big engine but will hit its power peak sooner, possibly even before 5,500 rpm in this case, which could potentially keep the big engine from reaching its true power potential.
The amount of power your engine makes is directly related to the level of volumetric efficiency (VE) it operates with-VE is the amount of cylinder filling that takes place per stroke, usually expressed in terms of percentage. Volumetric efficiency is probably most directly affected by cylinder-head port design, followed by camshaft profile. The biggest cam in the world can't force air past a restrictive port and into the cylinder (assuming a naturally aspirated engine), and conversely, the highest flowing cylinder heads available will seem only mediocre if the valves don't stay open long enough to fill the cylinders. This is why parts should be selected using more of a systems approach, rather than mix-and-match, or even bigger-is-better.
In your case, the cam specs you list are fairly tame, and your 350 probably will idle rather smoothly. The duration is a bit more than a typical factory performance cam, but the main difference is the lobe separation angle, which is a few degrees narrower than the factory would have spec'd for this engine. Still, the 112 LSA shouldn't cause so much overlap that the idle would be affected too significantly. This cam in a 455 would be fairly mild, and assuming good cylinder heads, would probably be the limiting factor in power production if big horsepower numbers were the goal.