From what I can tell total timing looks to be high 30s like 37ish , has the two silver springs and seems to come in slow. Initial timing looks like it's in the high teens
With out knowing alot of your engine stats I would say the total may be slightly high but that aint causing your issue. I would back it down to 34* total, pretty common. Im still thinking a fuel related problem, keep digg'n.
My 340 would flutter and skip with the stock fuel pump. An Edelbrock hi volume pump cured that.