Use the 8 blader on the R & tack weld an anticav plate behind it (between vanes/pump) & will need to cut a circular piece into 2 pieces (halves) to slip each half behind the vanes then weld them. I suspect you have more of an airflow prob & ;run the smallest WP pulley you can find/tight fitting shroud/MP thermal clutch fan spaced ~2/3 into the shroud/good aftermarket 180 stat tested in a suspended pot of water ahead of time & a 1/16" hole will help elim air pockets/easier filling/3 core rad/unobstructed air flow 2 it