ls motor question

[1968aj]

I am looking at a 70 c10 that has a 6.0 ls motor out of a 2005 chevy 2500. I have not heard it run yet. I never owned a truck with this type of motor and never would attempt such a conversion myself. if it runs right I may buy it. what should I look for to avoid a nightmare truck? it also has the transmission that came with the motor. this man selling it had it bult for his son and it scared him so bad he doesn't want it. is this a 4 speed overdrive automatic? any input is helpful. I will get some pictures tomorrow.