hey man, i just solved this on a 5speed which was the trans main shaft bearing and won't make noise with clutch disengaged but when in gear it does, right? that sounds like the trans main shaft bearing. but if it just start with your swap only, then it would have to be either something from swap or coincidence that main shaft bearing went out right as the swap happened. welcome to bring it by the shop and look at it for you. hope things go well.
