Engine Dieseling - Options?

I think I have figure out the source of my woes but over the years have realized that once you peak at frustration its often easy to overlook some of what you know is right so I thought I would share some of my source of frustration to see if I have overlooked anything.

my engine (to start)

Static and Dynamic Compression numbers were from a few internet site calculations and some comments here on the board

72 360 block - bored .030 over
pistons - confirmed TRW 11.5-1 (probably shaved some)
CC volume of cylinder calced out @ - 5
Head volume calced out @ 69cc's
Static compression came in @ 10.5ish
dynamic compression came in @ 8.3/8.4
Edelbrock airgap intake
Holley 750 DP with mech secondary's. (carb is stock now with 70-MJ and 80SJ and 6.5 PV)
Plugs Autolite AP66
Comp Cam - 247/254 @ 508 int/exh lift 108 lobe separation - cam degreed in at 106 ICL
Doug's long tubes
engine has pretty stable 9" vacuum
idle 1150/1200 (lose about 150/175ish in gear)

Currently have distributer set with the FBO plate locked at 12 degrees of mech timing, moved from 12 initial up to as much as 22 initial - still searching for the sweet spot - with full charged battery no issue on starting at 20 degrees initial - may be good at 22, but most happy at 18

I started the engine back around labor day - broke the cam in, changed the oil, pulled and cleaned plugs - engine sounds awesome - feels strong under the foot on the accelerator - had a few issues with brakes, alternator charging, etc. but the main issue is the engine dieseling when shutting down, still a few other issues to deal with once I get the engine where I feel good about hitting the street with it.

What ive done:

I tore the carb apart to confirm clean and what the jets were, primary was actually 73s, they were changed to the 70s that were listed as stock on Holley website, didn't try to confirm, measure, or change anything else

added fuel regulator to be able to make sure what fuel pressure was and no spikes

confirmed T slot exposure with carb off and set appropriately - no adjustment made after installed

changed to colder autolite 3923 plugs

added 6-8 ouces of octane boost (royal purple) just over 1/2 tank according to gauge - after adding the heavy dieseling slowed down a bit, moved the initial back to 20, car seem to like 18 as the best - easy start and idles good there - its a little rich and didn't try any adjustments

checked cylinder pressures engine slightly warm, all plugs out and carb open all the way through the plates - first few were 210 - 220 range - Not too bad I said to myself, realized battery was down on charge - after some quick charging - rechecked a few cylinders, looks like Im gonna be in the 225 to 235 range on all 8, stopped to let the battery fully changed and to get over frustration before setting the car on fire

My conclusion is that my dynamic numbers are off and I just need some higher octane fuel to run the engine, I have a preliminary thought on how to achieve but want to see if perhaps I could also tweak something, adjust something, or almost anything that I don't have to go and spend an assload of money on, I reran all my numbers on the same websites I got my original numbers from and it looks like if I could get 72 - 73 cc's on the head that could drop the dynamic down closer to 8 - does it look like Im heading in the right direction?

(this is by far my most long winded post i ever did - and Tim I would have sent this straight to you but your inbox is full LOL.)

I could have missed something I did or tried, hope the post isn't to hard of a read