OK, first. The bottom part of the article on my site was wrote by me. This is what I did to my old stock distributor. I'm the one who says to use both blue springs, not Damon.
Now, if you set the lock out where I have a arrow pointing to, you should have around 16 degrees vacuum advance. This is where you need it if you still have a working EGR. I think you don't have one, right? If you
don't have a EGR, you need to lock out all the vacuum advance you can, which will leave you with around 12 degrees. It just hit me what was wrong with your setup besides the springs.
So, first thing I would do tomorrow if I were you is first, move the lock out to the maximum lock out setting, which is all the way over to the last notch, not the second to last. Then check the timing and see how much vacuum advance you have. Should be around 12 degrees.
Test drive it. It may be fixed and not spark knock, without changing the silver spring to the blue. If it works this way, leave the springs with one silver and one blue. This will be best for performance. If not, swap out the silver spring for the other blue and try again.
I think the lockout will fix it. If it doesn't fix it, the blue spring should for sure.
Timing is an experiment. No two settings are the same for everyone. Even on the same type vehicles. Your truck is heavier than mine being a long bed. Timing is affected by weight, as is torque, stall speed of the converter, etc.
There is no one setting for total mechanical advance. It's a game of try and see. Every engine, tranny, rear gear, truck, etc. will be different. There is a close setting though. Then it's once again, try it and see what happens. Only true way to find out if it works, as in helps performance is to time it, as in on the strip. But you and I don't drag our trucks or have access to the strip, so it's a seat of the pants test.
Most all SBC's run best in the 32-36 degree range of total mechanical advance. A stock GM HEI has 20 degrees built in with the weights. So, with this in mind, it means you need 12-16 degrees initial advance. Vacuum advance is not for performance, but for economy and good manners on the street. Now, the rate of the advance is what makes or breaks performance. You want it to come in as fast as it can but without detonation (spark knock). The faster, the better. It's best if it starts right off idle (in the 800 rpm range) and is full in by 2800 or so. This is where the one silver and one blue springs are supposed to operate. Both blue springs will start around 800-900, and be full in at around 3200. I tried a silver/blue and it wouldn't work for me. I guess maybe with my EGR working, I don't know. It may work for you.
So going by this, make the changes I said to do to the lock out. Leave the springs with one silver/one blue. Set your initial at 16 degrees. Test drive it. If it spark knocks, lower the intitial to 15. Try it again. Knocks, try it at 14. Keep going until it quits or until your reach 12 degrees. If it still knocks at 12, change the spring to the other blue. Now raise the initial back up to 16 degrees. Do the same steps as before. Don't go past 12 degrees though. What you are concerned with here is not the initial amount of the timing, but the total. Never concern yourself with the initial. You want the most you can run and not spark knock. On the initial, all you are after is no spark knock at cruise and easy starting, especially in hot weather. All this my fly out the window next summer. Then it's back to the drawing board.
Try these stesps exactly how I've outlined them here. You will get it. Don't panic because this is not a quick process.
Mike