YES. Those 2 engines are the same. NO difference. It is a direct bolt in.
Which engine?
Yes
No they will not.
depending on model of truck.
yes you can you can put any engine in it that you want
Yes it will.
Your best bet is to visit a good auto shop (seller of antifreeze), and say "I want to buy enough antifreeze for a 1990 Chevy 5.7 truck".
yes, they should be identical.
passenger side of firewall in engine compartment
No difference at all.
That would be the 700R4
Yes, it is all the same.