As far as heads and porting go...

Going back to the Pontiac example because I'm familiar with it. The factory never published any flow numbers but enough people have flow tested factory heads and published the results that the info is readily available.  The speed shops who supply ported heads and aftermarket heads supply flow sheets that show lift at every point from .050" up to .550" or higher if needed for an all out racing application.  Flow is typically measured at 28" pressure drop but if done at less than that it's fairly easy to convert between the different pressures.  Therefore you can see how much  better a ported head will flow than stock.

Going back to Toyota - even though the stock flow rates aren't available, if we have a flow sheet from a ported head that can still be useful for helping to select a cam and estimating the potential power output of an engine.  For example, a head with a very high intake/exhaust flow ratio doesn't need a cam with extra exhaust duration unless you're trying to crutch a restrictive exhaust system, but why would you spend the money for head porting/flowing to saddle the engine with a stock manifold? 

Does the flow rate plateau at a certain lift point?  Let's say the head doesn't gain very much if any flow from .450" to .500" lift and again the gain is very small or non-existent from .500" to .550".   That tells us that running a cam with a whole lot of lift isn't really necessary.  Just puts extra strain on the valvetrain components, though keeping the valve at it's max flow lift for as long as possible is beneficial.  A custom cam grinder can come up with a "flat nosed" lobe that gets to a certain lift then stays there awhile.

It's interesting to me that most of the performance cams for these little engines are on narrow lobe separation angles (LSAs), usually around 108-110 degrees.  You posted some specs for some Schneider cams that went out to 112 and what I noticed with your dyno sim plots of those is what I would expect from a cam with a wider LSA - a flatter torque curve that starts earlier in the
RPM range but doesn't have quite as much peak torque.

This is what makes me REALLY want to see some verifiable info on the stock cams.  Most stock cams for GM engines from GM use really wide LSAs because they provide smooth idle and good low speed operation with broad torque bands.  Aftermarket cams typically use narrower LSAs, often a lot narrower, because if you're building a race car with a loose torque converter and steep rear gears you want to build the engine to make maximum power and set the drivetrain up so the engine stays close to its peak powerband while running down the strip.  Idle quality and low-speed torque and drivability aren't much of a consideration.

If the Toyota factory cams are on narrow LSAs, say 108 or 110 there could be several reasons for that.

Anyway, that's my brain-dump at lunchtime.   Gotta get back to work.