Broken Valve Spring - Which New One?

The tool rental spring compressors,fail every time. Tried both O Reilly's /AutoZone , couldn't handle 300 pound compression springs. Went with Napa/K-D tools part number,2078. It handles Rat Chevy springs,in the 400 pound open zone. Cam specs aren't really important. What is: installed height/ pressure at valve closed/pressure at full lift/maximum lift. Maybe some research on the LA based 380/360 crate engine,would find your answer.