I'm tired of racking my brain with how to fit 2 21" death penalties behind the back seat of my 88 s10 blazer 2 door, so I'm taking the back seat out! So here is my final question, sub and port direction? Subs and port up? Or subs and port forward? Or subs up port forward? Or subs forward and port up?

Why don't you just get some 18s or whatever that will fit? And if you're doing all this, why not just wall it? But most likely in a non-wall situation, either subs and port up, subs up port back, or subs/port back will be best. Anything forward in an SUV is basically never better unless it's walled.

Racking your brain on trying to fit 2 21" subs without removing the back seat? Easy man, just give them to me and buy some smaller subwoofers.

Only way to fit those monsters is to remove the back seat and hope the hell you still have enough airspace to build a proper enclosure for them. If not sell and downsize!