Wbulk Nice name
Let me see if I can clear a little of the info up here. First off, what is your car setup for? If there is one fuel line running from the tank to the fuel pump, your car was setup for a mechanical pump. They are dependable and should last for years. The main thing with these pumps are what the diapham is made of and what fuel will not bother the material. We are getting into more fuels like E85 and this is having issues with some pumps and lines. This is why most auto companies have gone to plastic fuel lines.
The plus on the mechanical is, the simple way it runs, it's quiet, and overall dependable. Down side is that you have to crank the motor to get fuel into the carb to start the motor. If the car has been sitting for a couple of weeks, the gas will evaporate and you will need an extented cranking to start the motor. This is also when the most wear on the bearings happen. If you have taken the car for a good drive and it is hot, unless you open the hood or have a turkey pan seal around the carb, the gas will turn to vapor and again you are with the long cranking to get the car started. On some carbs you have to pump the pedal 2-3 times before trying to start the motor and this also sets the choke operation. Depending on the carb you can easily wash down the cylinder walls from this starting way. I have had mechanical pumps last 100K miles I have one on a car with 144K and still working fine.
Electric fuel pumps, there are a couple of different styles, Pulse and rotary pumps. You can get them to pump from 6 psi to over 100psi. Depending location is about how much noise you will hear. A pulsing pump is quieter than a rotary pump, pulsing pumps due cause problems with some carbs and the needle and seat for keeping the correct fuel level in the carb. If not careful the pulsing pump will bounce the needle in the seat and overfill the carb and whole motor. I have seen this happen. You should have a regulator on this system between the pump and carb. Set to 5 psi. I would also put a return line in if you can to ease the pumps working load and better control of the fuel pressure. You will need to wire a relay to the igntion switch or use a remote switch to turn on and off. This pumps is not used on FI systems in general. They do last a long time, I have one for 6 years on my jeep that goes off road and it took a beating and no problems but the flood issue.
Rotary fuel pumps, depending on location, in some cars they are noisy. Weldons come to mind on my friend cobra mounted in the R/R corner of the car. It is a race pump and you can hear it at an idle. 15 years and runs fine with 30K miles on it. This is for a Olberg setup with #10 lines to the the carbs and #6 line return with a fuel regulator between the pump and carbs. Down side of this setup the pump doesn't draft well from the tank. The pump is low as possible and the tank has a sump with 2 #10 outlets. After racing for 20 minutes the fuel is warm from running from the tank to the carbs and back. Up side of the system, able to fill the carbs without cranking the motor, little cylinder wash down from this setup. Down side is location of the pump and custom fuel tank outlets. This pump had problem lifting gas 12" above the tank. It doesn't have great sucking abilities. The pump is larger than in the ta
nk pumps and draws more amps. It is rebuildable.
In the tank pumps, I have 2, 255liter walbros for my FI system. They are quiet when the tank is half full or better, I can prime my fuel system and then turn them off before starting. No failures on 10 years of running the same pumps. I do have a fuel pressure regulator set at 44 psi at idle and 52-54 at WOT. These pumps in the tanks need fuel to help keep them cool and extend there lives. Mine I only here on priming the system, rest of the time, no noise. I do have 2 couple fuel supply systems going to the front of the motor and one return line. I have way more supply than the motor will ever use. It is nice to have too much than not enough. These pumps will not work with a carb to well, too much pressure even with a good regulator.
Bulk you are running a SB motor in the car. a 3/8" supply line from the tank to the motor will be more than enough for your setup. I do prefer to have a return line on all my cars to help with the dead heading of the gas. I don't like this way of fuel system because of the small debries that get into the system and through or around the filters. Over time this crap ends up in the float bowls and jets for carbs, and in injector rails and injector screens on FI systems. If setup right both pumps will work fine. IMO electric is better strictly for the cranking issues of the motor. I also run a accusump as a peroiler before start my motor. Cranking with 30 psi in the motor is better than 0. Regulator, a good one and return line would be my reccomendations. This is from 30+ years of racing and being a wrench turning mechanic. Good luck. Rick L.