Carb backfiring

[bmg]

Man i need some help on this. Recently put a truck avenger 550cfm on my 70 350 30 over motor with rv cam and hei with 350 turbo. For the life of me i got a timing mark on it and well lets say i don't think its the right one cause its bout 33 deg off. this mark is to the right at about 2-3 o clock looking at it from the front. with a scope on it when it runs the best the mark on the balancer is right under the top of the water pump. now how in the hell can i see or put a timing marker there? is there any other way to tell if it jumped a tooth? also i have a clear fuel filter (big en) comin off the gas line just before it enters the carb, is this suppose to stay full all the time? i think that is why i am gettin the backfires cause there is not enough gas gettin to the carb. does this mean a bad fuel pump or somin else? sorry for all the questions but really need some help.

also anyone got a fabrication to that dam ac flapper in the diversion box or i gotta by a whole new box?