Warm Engine Idle Issue

Please help me from throwing in the towel. I already threw all the parts I could think of at it. My 318 stumbles at idle when it is heat soaked then sits at idle for several minutes (not hot outside here in S. California). Here's the details on the engine...

- Original 318 bored 0.020
- Original heads with larger valves (1.88/1.60)
- Classic Holley 600
- Weiand Stealth intake manifold
- Comp Cam 20-223-3
- Hedman long tube headers
- One 20 micron filter right before the carb
- 5/16" rubber fuel line from chassis to mechanical pump/pump to carb
- 18 deg initial, 36 deg mech, vac connected
- 11 inches of vac while in drive
- 68 jets, 4.5 power valve
- Mixture screws out 2 turns (highest reading on vacuum gauge)
- Carb float levels adjusted just under threads of opening
- Carb heat insulator spacer installed
- Idle set at 800 RPM
- Curb idle set to where I am still on the idle circuit
- Spark plugs read good. Almost a full turn of color on the base with no heavy soot. Porcelain clean.
- Compression check is 135 PSI on all cylinders with no vacuum leaks.

I have swapped out the distributor, rotor, cap, wires, coil, module, ballast resistor, plugs, and fuel pump with no changes. I also rerouted the fuel line away from the hot areas. Nothing seems to help. I ordered some insulation sleeves for the fuel lines today in hopes it may be from vapor lock. When it is stumbling, I look down the carb and the fuel squirts in normally. I figured if it was vapor lock it might spit abnormally. Idle/mixture screw adjustments have no affect while it is stumbling as well. Timing is steady. Any other ideas for me to try while waiting on these insulation sleeves? Thanks for your help. This is the final discrepancy I need to work out with this car and I can finally relax and enjoy it.