350 Running Problems

[Doomguy]

Hello
Ok here is the deal,I have a 49 Ford Coupe with a 1972 350.Last year a mouse
had chewed threw the rubber fuel line so
the tank sat empty for about 6 mo.I put new fuel line on and it was fine for a while.Then it started running like crap,backfiring through the exaust,no power.I thought it was timing. I have replaced the Fuel pump,timing chain,put in HEI,all new plugs and wires,cleaned out the Elderbrock 600 cfm carb(new last year).It was fine for a while,now its doing it again.There seems to be good fuel pressure,compression test was also fine.
I also put 2 fuel filters,one befor the pump
and one after.At high rpms it seems fine but it hesitates when u punch it and it backfires out the exaust when you let off it
PLEASE ANY HELP!! I realy want to take it to GoodGuys this year.
Thanks