Hey there gang!

What would a stock 1979 L48 fuel pump put out in terms of PSI and GPM?

Would it make sense to go to an aftermarket pump, such as an edelbrock or a holley since the engine is pushing somewhere around 400 HP?

Would the stock pump provide enough performance?

Also, How would you transition to an aftermarket pump from the hard lines where the molded rubber lines start (feed and return to the tank)?

Do aftermarkets have a return?

I know I have several questions, but understanding appropriate fuel delivery is a weak subject for me.

Thanks crew!!

Luke

LukesVette38752.8735185185

Stock, mechanical pumps put out around 6-9 psi, normally. There are some that pump a little more, but most of them are in this range. Don't know for sure on the gph rating...would have to look it up.
If the engine is running well as it is(fuel-wise), the plugs are not melting, and there is no detonation(pinging), you're probably OK with what you have. Always room for improvement, however!
There are aftermarket mechanical pumps that will bolt right on in place of the stock pump, and allow the use of all of the facory lines. They put out about the same pressure, but a little more volume. I think Edelbrock makes one, as well as Holley. Electric pumps normally do not have return provisions, therefore you would need a fuel pressure regulator, to keep the pressure in the working range of the carb float/needles-seats.
You can mount an electric pump in the rear, and run the rubber line from the tank to it, and then out to the hard line on the chassis.

If you do choose to go with an electric, check the vacuum the pump draws.  Some electrics will pull vacuum, but many will not pull very well.  This is not a problem.  Just mount the pump near the fuel tank instead of up front.  An electric that pulls poor vacuum can fail to get the fuel from the tank, and cause starvation problems.

You can still put the regulator up front.  This would keep fuel circulating in the lines and prevent heat build up and possible vapor lock.

Electrics are a good choice.  But many large block high HP engine run very well on high output mechanical pumps.

Choices, choices.