Questions about swapping s13 into s15

[3inchs]

My buddy has been wanting to swap his NA(SR20de) Auto spec c s15 to a 5 speed and an SR20det. We found an s13 that still has the sr20det and 5 speed with a dual disk for $500. Im thinking the only hold up with the swap would be merging the wire harnesses. Does anyone have any insight about this swap?

TL;DR is an s13 sr20det and 5 speed worth swapping into an s15 na auto and is it going to be a pain in the ass?

[TheRealSy90]

Wiring Specialties can make you a plug and play engine harness for that engine and trans in that chassis. Easiest option.