1948 pontiac 6 cl getting too hot(215deg) in just a few blocks of driving

I would suggest doing a cooling system pressure test. You can get a loaner test tool from any Advance Auto or Auto Zone.
It should hold pressure and take some time to leak sdown, just as a compression test but it should hold pressure longer.
That will let you know if you have an intake gasket or head gasket leak or maybe even a crack in the cooling jacket of the block.

The pressure test was done by the same shop that did the dye test and it checked out fine, also the block was magnafluxed at the machine shop for cracks,there were none.I also removed the temp coil flaper under the exhaust manifold not sure the right name for it but it helps cold starts.

The part on the exhaust is called a heat riser.
You might have an air bubble in the system.
Try bleeding system by turning the heat temperature all the way to hottest so the heater core is fully open. Then top off and let it reach operating temp. Then drive then repeat and see if you can get any air out of the system.

IS YOUR LOWER HOSE S.UCKING FLAT?

NOW A DAYS, THEY AIN'T PUTTING IN ANTI-COLLAPSE SPRINGS

I HAVE BEEN SEEN SNATCHING THEM OUT OF THE OLD HOSE AND PUTTING THEM INTO THE NEW ONE.

IF YOU STILL ARE GETTING NOWHERE---DOES IT OVERHEAT W/ NO THERMOSTAT?

ON "WILLY" AND MY OTHER JEEP CJ TOO, I STARTED USING "SUBARU" STATS ....THE MOST COMMON ONE THEY USE HAS THE SAME OUTSIDE DIAMETER AS MY TWO JEEPS ('46 AND '77).....THE INSIDE OPENING IS THE CAT'S MEOW, FLOW IS GREATER THRU THE GIANT HOLE! I HAVE PICS OF THE OEM (LEFT)NEXT TO THE SUBARU (RIGHT)

SORRY, I CANNOT FIND THE DARN NUMBER! I SAVED THE BOX LID SOMEWHERE.....IF YOU ARE INTERESTED I WILL GET IT FOR YOU

THE MEDIC