G'day Wayne,
I'm guessing that after the car sits for a week, you have to crank it over forever to get it to fire? This could be due to leakage (the drips from the carb can be subtle), or could be the fuel bowl evaporating over time, leaving the carb dry (the fuel bowl vents to the carb throat, which in turn vents to the air cleaner and from there to the engine bay). Mine does the same thing, though takes about a month to dry the bowl. As a quick check, I'd suggest letting the old girl sit for a week, then take off the carb air horn and visually confirm the bowl level is dry.
If your fuel pump is on it's way out, it can take forever to reprime the bowl. You can check the pump with a tee-piece and pint glass (as per the workshop manual), but this is not so easy if you still have the original steel fuel lines (easier if they have been replaced with rubber hoses).
An electric pump may not help the issue if it is "loss of fuel bowl level over a week causing hard starting". The stock factory pump will prime the bowl pretty quick even from stone empty.... not much slower than an electric pump. The electric helps you out by being able to switch it on before starting the engine. This is fiddly - you need a fuel pump switch in the cabin. It is also reccomended to use an electric cutout that stops the fuel pump with low oil pressure or loss of ignition (Peel Instruments makes a black box, commonly used in LPG conversions). Add to this the power and mounting for the electric pump and the noise fro th electric pump, and the pain-in-the-bum factor gets pretty high.
If it was mine and I was determined to replace the fuel pump, I'd buy one of the new red motor mechanical pumps available. Not much help if you are running a vacuum pump admitedly
If you do absolutely want to go electric, the info below (culled from the Stromberg and Holley 350 Guides) may be handy:
Stromberg carburettors operate on approximately 2½-4½ psi of fuel inlet pressure (SUs are happy to run on 1½-3½ psi and overflow around 5 psi, and 350 Holley carburettors run happily at 5-7psi). Too low a fuel pressure and the fuel level drops in the bowl. Too high a level and the needle and seat is forced open, flooding the engine. This is a particular risk when the original Holden mechanical fuel pump has been replaced with an electric inline pump – see chart and table below. When using inline fuel pumps (notably Holley), a pressure regulator is mandatory to prevent flooding.
Fuel Pump Maximum Pressure (psi) Free Flow (GPH)
Facet SS208 3½ 14
Facet SS171 3½ 14
Later Holden (blue motor steel can) 3.9 9½
Facet SS500 4 25
Facet 60104 4 25
Facet IP002 4 32
Early Holden (grey/red glass bowl) 4½ 9
Facet SS148 4½ 24
Facet SS501 4½ 30
Facet SS165 5 15
Carter GP4600HP 5 100
Facet STS504 5½ 30
Facet IP007 5½ 36
Facet IP131 5½ 36
Facet IP220 5½ 36
Facet 60106 6 32
Facet SS135 6 34
Carter GP4603HD 6 43
Carter GP4070 6 72
Facet SS502 7 32
Facet STC505 7 35
Facet IP051 8 30
Facet RTW506 8 40
Facet BTP001 8 40
Facet BTP001 8 40
Carter GP4594, GP4389, GP4259 and GP4602RV 8 72
Facet SS200 9 32
Facet SS503 10 34
Facet 60107 10 34
Holley Red 10 100
Facet SS185 11½ 29
Facet 40222 11½ 33
Facet 40223 11½ 33
Facet 40237 11½ 33
Carter GP4601HP 18 100
Holley Blue 18 110
Holley Black 18 145
Cheers,
Harv