Before, and it really depends on what you are calling "modified" if you put a "hotter" cam in, sometimes the stock timing won't do it justice. You have to play with the timing and see what works best. Usually, advancing it 1 or 2 degrees gives the best result.
The timing will be 8 degrees before top dead center i believe although my 86 2.8 says it is 10 degrees before tdc
16 degrees before top dead center
Stock timing is 6 degrees before top dead center.
15 degrees before top dead center
8 degrees BTDC-- Before top dead center.
6 degrees before top dead center.
8 degrees before top dead center
8 degrees Before top dead center.
Generally 4 degrees before top dead center with the vacuum advance disconnected.If you have access to an advanced timing light then 35 degrees total is ideal. All manuals refer you to the sticker on the radiator cowl......There it states that the base timing is 6 DEGREES BEFORE TOP DEAD CENTER (DR).
6 degrees BTDC. ( BEFORE TOP DEAD CENTER)
12 degrees before top dead center.
6 degrees BTDC / Before top dead center