They are Chevy 305 & 350 TBI Throttle Body Injection cylinder heads 1987-1995.
Not a Good Head for Hotrod or Race Use.
1st Hand I can say they do work nice in Chevy & GMC Trucks where you need lots of off idle torque & Midrange Power like for 4x4 & Towing duties.
Swirl Port Chevy Iron heads the 191's are.