Steve Blackman did some shotokan karate, tae kwon do, and escrima according to wikipedia. I don't know how much he trained in them, but, some. That's all the martial arts training he had outside of professional wrestling.
Ken Shamrock on the other hand had tons of martial arts training. He wrestled, did toughman boxing, he did underground streetfights, he did shoot-style puroresu in Japan, he was the King of Pancrase, competed in many MMA fights, and has refined his MMA style too with different moves.
You have those two going head to head it's a no-contest. Shamrock would definetly beat him in one round. How he would do it would be the only question. He would probably put him in a submission hold and make him tap out since he is a submission specialist.
SHAMROCK 2:00 ROUND 1 VIA SUBMISSION HOLD OVER STEVE BLACKMAN.