Heyya!
Thank you very much for the well-sourced feedback, that is helpful. Let me address some of your main points.
OHV maximum RPM speed is really slow
I think you are referencing solid lifter setups, which of course do rev a lot higher, those are not the one in game though.
cost is very high exceeding DOHC 4 valves
I can’t confirm that at all. In an example engine I have $620 material cost for DOHC-4, $566 for OHV. 22.5 production units vs. 15.5 and 35.8 months engineering time vs. 24.7. The pushrod engine will be A LOT cheaper to produce and engineer. Maybe you are playing the Kee engine version and reference MOHV? That has been removed from the game in the UE4 version. For that the material costs were higher due to the fancy materials used for the valvetrain of modern LS motors.
octane rating is very high
Yes, and compared to other engines it should be due to the less optimized path the air fuel mixture has to take to get into the combustion chamber. That is an OHV and DAOHC issue. If the compression ratios overall are too low is arguable though.
Please note that because of American automotive history, they are obsessed with OHV engines and their tech does NOT reflect the norm. In order to build anything American style, assume that you need to put about +10 quality into the top end section. That is about where the US manufacturers were in the 60s with their OHV setups.