How close is your tune up specs to those of a stock 1954 223 / with Auto trans (see below)?
1. Plugs gapped at .035
2. Point gap set at .025 or better yet at 36 degrees dwell
3. Base timing set to 3 degrees or up to 6 degrees BTDC
4. Engine warmed up good intake and exhaust valves lash set to .015
5. Mixture setting at lean best idle i.e. Engine warmed up good then Tuned to Highest RPM the mixture screw turned in 1/4 turn.
5. Idle RPM 450 with engine warmed up good air cleaner installed, trans in drive with emergency brake set.
Compression Test should be a minimum of 120 psi
Fuel pump test 3.5 to 5.5 pressure. Have you done a fuel pump volume test yet. How's the condistion of your Holley carb? Float level set correct, check condition of the power / economizer valve too. Have you checked the intake manifold and carb base for vacuum leaks?
The Load O Matic Distributor timing advance settings should map at these amounts.
500 RPM 3 1/2 to 4 1/2 at inches vacuum of .50
1000 RPM 8 1/4 to 9 1/4 at inches vacuum of 1.8
1500 RPM 11 3/4 to 13 at inches vacuum of 3.8
2000 RPM 14 1/2 to 15 3/4 at inches vacuum of 6.0
How dose the coil check out on primary and secondary windings? A quick test have a nice blue spark that can jump 1/2 to 1 inch gap holding the center coil lead away fron coil tower and to each spark plug using some insulated plairs to hold the wires away. It's rare to have happen but a bad or even just a loose screw in the mounting bracket of the condesor to the point plate can cause your semtion's too. Good luck