340 demon overheating problem

22" original size will work fine! i have about 420hp with 11.2 to 1, 4 core rad, 5 blade 18.5" fan out of a mid 80's diplomat, clutch from Napa ask for a 78 pontiac sunbird one, with a 305ci, an original shroud, plus i run a 50/50 mix. I tried the elec fans, on the street MOST stink.