Welcome to CHR. I'm not following what you've done so far. Your brother bought another engine, but did he get the computer and the engine, chassis and interior wiring with it or just the engine? Did he do a R&R on the engine, or just swap the heads, intake & TBI from the "new" engine onto the old? Not following why an adapter plate was needed - why not just use the heads, manifold & TBI as a unit as opposed to mixing parts old & new?