What are normal engine coolant temps? Need help with intermittent overheating

[MAC]

I have read that 2-3 5mm holes work, but I would def research a bit before so. Theres tons of info on it. I am not sure on the heater core, but in the morning I can take a look at my truck and see. Can post some pics if needed. Ive attached a file of Fast's go to timing table for vortec heads that should get you going in the right direction. Probably just minor tweaks from there

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Some photos of how my heater core is connected. (Please don't judge the lack of wring harness loom - this truck needed a lot of love and is work in progress). The hose closest to the drivers side (on right in photo) is connected to the intake manifold. The hose on the passenger side (left in photo) is connected to the radiator just below the rad cap.