Any manifold/carb setup benefits from having the "heat dam" insulator gasket, but that is certainly not anything that keeps the motor from running! You can add that anytime, felpro 60677, we got 'em in stock! That is a workaround for reducing the phenomena known as "percolation".
All the IH sv manifolds are what we refer to generically as "medium/high rise". That is a performance-enhancing feature for a truck engine and is something that all the aftermarket manifold manufacturers offer in their performance lines ups. Your manifold is also referred to as a "dual plane", again, that is a performance feature. One more reason why none of the aftermarket folks ever made manifolds for these motors, they didn't need it!!!! The rpt aluminum manifold is nearly half the weight though compared to the cast iron unit, and significantly increases heat transfer away from the intake system.
That manifold is not the "earliest" version however. Yours has the cut-away section under the throttle linkage area that allows use of several aftermarket carbs without the need for a spacer to allow throttle clearance.
Also, your water neck is the earlier style used on some pickalls and the first year Scout 810/Scout II. If all the stuff is original to that motor, it would be "correct" (if the pcv is connected) for a m/y 72 Scout II app based upon the motor mounts. Those used that non-egr intake and the Holley 2300. That manifold uses what I refer to as the "vacuum tree" setup at the rear of the plenum. The sheetmetal surround on the passenger side exhaust manifold is for the heated air intake tube to the air cleaner snorkel, I'd remove that now while it's easily accessible.
The pertronix unit is unique to that prestolite distributor only, they are not universal. Each distributor type requires it's own dedicated p-tron if ya chose to use one.
All in all, what ya got there is a total non-emissions setup, very simple to deal with as it has no add-on gobbledeegook!!! My kinda motor!