I read here all the time about guys setting there initial timing 17-18 degrees. I have a 396/325 stock for the most part. Which is suppose to be set at 4 degrees initial (Vacuum disconnected) which will give me approx. 38-40 degrees total. Right ? What goes here ? Confused!

The stock timing is usually something like 4-8 degrees BTDC initial on a big block, which is much less than optimal usually. Many big blocks like around 12-16 degrees BTDC initial w/vac disconnected.

For the total advance, the stock setup varies, they use certain weights and springs to give a certain amount of advance. You have the additional mechanical advance which is added to your initial to give the total. My 402's stock distributor had something like 16 degrees mechanical, so with the 4 initial it only had 20 degres total advance.

I just had another distributor redone, and it is setup for 20 degrees mechanical advance all in @ 3,000 RPM, combined with the 16 initial I'm going to run it'll give me 36 degrees total, which big blocks tend to really like.

Hope this helps and makes a little sense.