20V MK1 Engine Swap Using 20v Fuse box

20V MK1 Engine Swap, fuse, motor, harness, silvertop, receive, happened, body, power, supply, 100%, means, mine, idea, stock, encounter, mechanics, issues, bought, shop, swap, regularly, buddy, owns, lied, face, thinking, auto, problems, wiring, manual

So me and my buddy who owns his own shop and does swap somewhat regularly (never a JDM motor though) are having problems with the wiring. It is a manual silvertop motor and ecu with auto harness (guy I bought the harness from lied to my face). We were thinking about using the old stock fuse box and the silvertop fuse box (I happened to receive it too) and supply the power to the body and ecu that way. What issues do you think we will encounter? p.s. this is my mechanics idea and not mine so