40 degrees initial!

Hello, FABO. As you can tell by my avatar I'm normally over at the sister forum but I run a 340 in my 72 RR and figured there are more small block experts over here. I run my 340 now at 20* initial, 38* total all-in at 2400 rpm or so. Hughes 2832 cam .228@50 .530 lift. I wanted to see where she "wanted" the timing. I turned distributor to highest, smoothest idle. I was at 40 initial!! Lowered idle back to 850-900 (that's where I need idle) and kept going. Again, she was happiest at 40 initial. I don't run any vacuum advance (I only have manifold port on my AED 750DP and can't get rid of off-idle stumble with vacuum hooked up. I make 9hg at idle in gear. Tried many times. So vacuum advance may not be an option). I'm trying to avoid a locked down distributor (plus, hot starting I'm sure would be an issue at say 38 or 40 initial). Hot starting is no issue at all at 20* initial. Any suggestions to make motor its happiest with this situation? Thanks