91 to 87 motor swap???

What issues will I have, when I put a 305 TBI and O/D tranny from a 1991 3/4 ton chev van, into a 1987 gmc 1/2 ton pick up, that had a 305 TBI? Are
the computers the same? Will the oil pan need changing? Motor mounts etc..? Any help would be appreciated.
Thanks Mike
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