I know the obvious difference in the two, but can someone give me more of a reason that injected wont be a viable option for sbc's

Enclosed engine compartment dictates water jacketed.

too much heat buildup I assume?

injected headers do not have any water to them below around 1500 rpm so they are hot at idle, even when up and running they are hotter to the touch than jacketed headers. my jet boat and v-drive run injected headers but there is no cover and the engine is out in the open. coast guard and insurance dictate that you not catch the boat on fire due to hot headers with an enclosed engine bay.