Engine:
440 bored .040"
Flat top pistons/Zero Deck
.039" Thick head gaskets
915 heads with over sized valves and harden seats/milled slightly
11:1 compression ratio (4400' altitude)
1.6 Roller Rockers
Comp Cam XE285HL-10 Duration @ .050 241/247
Lob lift .364/.364 LSA 110
Stock steel crankshaft
440 performer manifold set up as true dual plane/1" phenolic spacer
Holley 870 street avenger (went two jet sizes lower per Holley for altitude - 76 primary/80 secondary)
Hedman Headers 1 3/4" tubes

Ignition:
MSD6AL
Mopar Performance Distributor

Questions:
From what I have read Total Timing should be about 36 degrees.
I have the initial timing at 18 degrees and it runs and starts fine but when the vacuum and mechanical kicks in (2500 rpm) my total timing is 48-53 degrees.

I tried turning the vacuum advance adjustment with a 3/32" Allen wrench clockwise (first source I read) and went one turn at a time until it bottomed out. NO difference. So I backed it out to where it was and then went another full turn counterclockwise but still no change.

My thinking is that the vacuum advance is not the problem but rather the mechanical.

Is welding the slots the only way to remedy this situation?

Sorry for the long post.