The story at the top, question at the bottom.

Two weeks ago I got a Cuda with an odd "overheating" problem.

I bought it from a guy near Eau Claire, drove 350 miles home... 10.5:1 494 RB, Quick Flow 950, Victor 440, Performer RPM heads, 268° solid cam, 4 speed, 3.73 dana, 295/65/15 rear tires...

On the interstate it stays at 180 F @ 50 mph, 60 mph, 70 mph, 80+ mph.

Cruising on back roads at 30-40 mph it stays at 180 F.

"Spirited" driving up to 7500 rpm it stays at 180 F.

Idling 1-2 minutes it stays at 180 F... then the mechanical coolant temp gauge starts to "twitch" from 180 to 210...

Turn off the engine after idling 1-2 minutes and the temp gauge continues to "twitch" from 180-210 F and you can hear it boiling in the pass rear head...

Wait 5 minutes and you can remove the radiator cap and it does not push out any water.

No coolant in oil, compression 150-155 psi on all cylinders, plugs all look normal.

Pressure test cooling system to 15 psi it will hold for hours...

Play with ignition timing from 30 - 38 degrees total... no change

Drill three 1/16 holes in 180° thermostat ... no change

Change from 16 psi cap to 7 psi cap to 13 psi cap... no change

Change to 160° thermostat... same behavior, just runs at 160° instead of 180°.

drill two 1/8 holes in 160° thermostat... takes longer to get to 160, but no change.

Currently has a "AC Delco / Rock Auto" 6 blade stamped steel impeller water pump with the a flat metal "anti-cav" plate on the back, it has over 0.100" clearance between the blades and the proflo aluminum housing

Crank pulley is 6.5" diameter
Water pump pulley is 6.75" diameter

I am ordering a flowkooler 16 blade pump, but also want to OD the water pump 10-20%

Where can I buy a 5.5 to 6.0 diameter water pump pulley for a non-A/C RB Mopar?

Thanks

Craig