It will also help clog up your heater core and radiator. Stay away from that garbage. If you have electrolysis build up (like many of these do) in your head and block, pour that junk in there and youe almost guaranteed to be doing a head gasket soon.
That being said. My 80 model had a cracked block since about 83-84. The man I got it from cleaned it with a wire wheel and put some marinetex on it. Still there to this day. If I were in your shoes I'd clean it very well, mix some jb weld (the 4 minute kind) let it set over night and roll with it. I used it on a 5.9 cummins block in a pinch to get it home and as far as I know the man is still running it. Been a few years back since I talked to him.
