Running rich? timing off?

[gavinmosher]

Alright guys got a 84 c10 with a mid 70s model 400sbc in it... i need to get the carb tuned down a little bit it seems to be running rich there is puffs of unburnt fuel coming out of the exhaust. i am new to the carburated trucks and cars being a young gun lol.... as the title says i have a holley 750 doublepumper. and was told the truck has a cam. there is a possibility it is off timing a little bit too but i cant for the life of me find a timing mark on the harmonic balancer.... any help with either of these topics would be much appreciated..

thanks
gavin