Engine swap 5mge for 7mge

[eternal genome]

so me 86 supra is nice and all but i want a 7mge engine for it. Well, when the 86 was released, there were 2 models one with a 7 and one with a 5. If the frame is still the same except the engine in the 7 model, wouldnt it make sense that i could just put a 7 in a car that has a 5? also, does anyone know, im a noob by the way, what it means when my volt light turns on. I like my car so i drive fast and when i accelerate fast, my volt meter runs toward 18 and a red light comes on. BUT, when i drive at night and my lights are on and i press the clutch and brake, my volt meter geos down to about 10-11, and my car dips below 500 rpms then comes back up.

another question: my battery shifts in its little tray and when i take a turn it will slide and sometimes when it does my car shuts off. Then i get out, pop my hood and pull the battery back over to the left side and it comes on. what do i do?

Last question: I smell exhaust vapors in my car when i drive, and i smoke and i dont want to die. SO, do you think its a leak in the exhaust, muffler, gas tank, or what?

I need help!