fuel pump issues, I think. change to Electric or better mechanical?

I have a 1974 454cid, stock save for HEI with Accel top.
I just had the carb calibrated and the idle screw won't adjust. I can turn it in or out and idle does change a bit. Carb is a 625?cfm Quadra-Jet.(stock with rebuild 10 yrs ago)
It won't get up and go unless I feather some gas in prior to full throttle.
I think my fuel pump is weak.

I am being told to step up to an electric pump but I have original wiring in the car and I am not sure I should be adding any more electrics in. What is the pros cons to mech fuel pump from Carter or Edelbrock(10psi) vs. an electric fuel pump?

Not that it matters but the car is a 1966 Chevelle Malibu

Hmm. OK, so I think I would rather step up to an Edelbrock Carb and manifold combo (performer intake with Thunder series carb) instead of farting around with the Quadra-Jet.
Keep the stock fuel pump?

Thanks DennyW!
You are a great source of information for us newbies!

By the way, did you mean idle screw or idle mix screws? The idle screw is on the side linkage and adjusts the idle speed. The mix screws are on the front baseplate. Some of these old smog carbs had either sealed screw holes OR a plastic cap over the screw. You could turn the plastic cap 'till the cows came home and never change the mixture.... I doubt that any caps have survived 30+ years on a carb but......

mike in tucson

I have always run electric fuel pumps and never had a problem. Both are S-W pumps and I do carry a spare, just in case. Some people prefer a mechanical pump because if in the event of a failure you can get a replacement at many auto parts stores. A matter of personal choice is my opinion. If you have had no problems with your mechanical up to now, then it probably would be best to do as Denny has suggested and that is to replace the old one with a new one now. You could always carry the old pump as a spare, if you have room for it.

Denny is also right about the fuel psi at the carb. 5 psi would be ideal anything over that will cause problems. New carb and intake would be good.

robot, yes, sorry, Idle mixture screw. It is on the front right as you look at the carb. I can turn it all the way in or all the way out and the idle remains constant.
Anybody have any thoughts on the Edelbrock performer 2.0 and Thunder series carb?