I had a griffin radiator for several years with differ small blocks both mech fan(5 blade clutch fan) an electric fans(dual from the junkyard) no leaks never over 190 deg in head or 170 deg in intake.
When I went to a 489 BB 2007 I went with a alumitech(no longer in business) aluminum radiator and dual spal fans on a shroud. Also installed a powermaster 140 amp alternator with new wiring sized for the higher output.
Usually temps stays 180 deg in head in line up traffic and 185 on highwaydriving on some days with 90 deg or more and long trips 150 miles+ and heavy traffic I have seen 190 deg or slightly more.
Is your temp in intake or heads? Can different as much as 20 deg. Head reads higher.
Same to all that has responded with temps is your temp in head or intake? Some are not so great if in intake imho.
Are you sure you have enough power for the fans?
No electrolysis going on? Just a thought since you are on your third leaking radiator.
Electrolysis: What it is; How to Test for it; and Ways to Prevent it
A good 2 row Aluminum rad with at least 1” rows is about 20-30% more efficient than same size 4 row copper/brass radiator.
Dewitt or cold case seems like good option if you want aluminum rad and they should last long time if your fans are mounted so they dont flex or move and cause leaks wich they will on any material if they are moving around or you have no electrolysis going on wich will cause leaks like you described.
Since you have 70 with lots of room and orginally came with BB you havnt thought of trying a 7 blade clutchfan and a oem or repro plastic shroud with a direct fit alu radiator from someone like dewitt or cold case? Or are you running serpentine setup so you dont have enough room? Only reason I went electric fans with my BB was lack of space 64’s dont have near as much space as a 70 for a good mech fan.