1st Gen CRX's take a LOT of work to swap anything into.
As my general rule, if you have to ask how hard it is, it's not for you.
That said, one of the "easier" swaps to do is a black or brown top D16 [or first gen ZC] from an early integra. Shoehorning a B-series into a first gen is not for the faint of heart.
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-Harry
AIM: NDcissive
CRX and Pre '92 Civic, Engine Tech and Tuning, & Track and Autocross Forum Mod