360 Idle Quality

Working on a 1965 Dart with 360. Problems with low idle vacuum, especially in gear. In gear, the most vacuum I can get is 9 in at 850ish rpm, and engine is struggling against the converter. The vacuum advance is just starting to come in at 7-8 in and would be all in at 14. I have slowly increased initial timing to 32 degrees (mechanical advance limited to 16) and I’m afraid to go farther even though every increase has helped. In park, the vacuum goes to 15 in and rpm jumps to 1400.

I have measured the cam at 278/291 duration at 006 and 0.300 tappet lift. IO at 28BTDC and IC at 70ABDC. EO at 67BBDC and EC at 44ATDC which makes the cam 106 LCA and 4 degrees retarded.

Don’t know the converter specs, but it seems too tight for the cam, at least for the retarded install.

I’m shocked at the 32+16=48 degrees total timing not causing issues under load, but it runs pretty good at mid/high rpm. Low rpm seems a little sluggish, but advancing the timing has helped.

Here’s my questions: Anyone ever seem total timing that high?
If I advance the cam, how far should I go?
I have a new B26 vacuum advance canister that comes in at 5-7 all in by 12. Any down side to installing it?

Other specs:
Looks like stock 1985 bottom end with stock dished pistons.
Compression ratio estimated at 9-9 1/4 (stock 8.4 compression, stock 73cc heads replaced with 63cc heads)
Cold cranking compression 130-140 (6 cylinders at 140)
Edelbrock RPM heads
Edelbrock RPM Air Gap
Edelbrock 650 AVS (have also tried 650 Holley)
MSD Digital 6 with Pertronix dist
New Autolite plugs gapped .045 and 8.5 mm wires
TTI headers and 2.5 dual exhaust
904 transmission with RMVB
8 3/4 with 3.91 gears