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You aren't going to use the original intake on anything but a LT1 / LT4 heads and block.
If you don't use the intake and opti spark then you can't use the original computer and wiring ;
so you need custom wiring and computer or a carb in which case anything that fits.
LSX conversions are popular.
You can put in anything that fits(even something that doesn't) with a little extra work but do you want to?
If you are going for a driver it is much better to go with the correct engine. If you are going for the challenge or shock value then a BBC or LS swap is cool but to just go to an earlier SBC doesn't make much sense.