spark plug recommendation
Keep in mind that this is just a recommendation, not a mandate; but, I'll have to agree with "71 Nova" about AC 44 or 45 heat range plugs. I'll go one step further and tell you that I use AC R45S or R45TS sparkers in all my Chevys from mild to wild depending on the requirement of the plug boss. I have a '79 Chevy 1/2 ton pickup that has specs pretty close to your engine and I run the AC R45TS plugs in it without any complaints. Those babies are always tan on the insulator shells no matter how I drive. I also run the same plug in my '67 Nova SS (slant plug 202 heads) and get about the same service as I do in the '79; but the Nova is barely streetable and certainly not an everyday driver. I think the AC plugs are a good bet for any Chevy V8.
Now about that timing, who knows? I usually push it as far as I can on the gas I'm using without getting into detonation (pinging, death rattle, etc.). I have the '79 pickup set at 8 degrees initial adavance and run it on the highest octane stuff I can get at the pump, which is usually about 91 or 92 in this part of Oklahoma. I run the '67 Nova SS at 12 degrees initial advance, but I use 104 octane avgas to satisfy it. I really don't drive it that much, so I can justify the use of such an exotic fuel. If I did drive it regularly, I would probably have to knock the initial lead back to about 4 degrees or less to keep it from pinging. And about total advance and knowing when it's all in, I never have known that in any detail on any of my engines. Mostly I time 'em by ear and seat of the pants, and only get the light out on the tough ones like Fords with EEC-IV.
Randy