Hello how's everybody I have a 1970 chevy impala with a 350 edelbrock intake and rochester 4barrel and no power up hill it all most dies out when u step on it and it backfires therw the carb and picks back up can anybody help thank you .

Backfires sounds like a very lean condition. I suspect a part clogged fuel filter, or just a weak fuel pump.
Either way, a very cheap fix for that car.

I was also remembering a time I owned a 69 Chevy with a 327. When I got into it, it would pop continuously through the carb.
It turned out to be cam lobes were flattening out causing not enough exhaust gases to leave the combustion chambers and exiting back out the intakes.
A compression check is always a good idea on older vehicles.
I found out recently on my classic Pontiac with a simple compression check, that cyl #1 & 7 were only running at 50% of their full potential due to detonation problems.
This saves a lot of guess work. We already know it's teardown time. Fortunitly, I have a fresh 455 in the waiting to go in there. :)