Weird transmission sounds Please HELP!

I bought a b16 cable transmission off a guy, now when i put the rod in to manually turn the tranny we hear sounds from inside like a clunking noise, could this mean theres a grind? or its blown? My motor is going in soon so should I take the chance of it being ok? or should I use my LS transmission instead? I really dont have the cash to get it checked out.

long shot but maybe something inside is broken or loose and bouncing around id play it safe and open her up