Cam sizing

What is your static compression going to be? My brother in law put the .508 in a 8.5:1 340 w stock converter and 3:23 gears. Only 100 lbs of cylinder pressure. Biggest dog you ever did see. Not to mention it wouldnt idle in gear. Instead of going the easy route and selecting a diff cam he chose to buy a 3000 converter 3:91s and it was still a dog because of the lack of compression. Eventually he put on some closed chambered heads w thin gaskets to get the compression up to 9.5:1 and we advanced the cam to 104 to get the cylinder pressure up to 140 lbs and it now goes pretty good.