Put a red rag down under the float bowl.
Place a cleaned out small tuna can under one of the screws.
Drain the gas out of the float bowl into the tuna can then do what the guys have said.
(Helps to put a light pinch in one side of the tuna car which makes a nice pouring spout.)

What has led you to a jet change?

Imo, you'd be better off with a vacuum secondary Holley on a street runner.
Or a 750 Edelbrock/Carter if you like those.

I don't want to get into an Edelbrock/Carter vs Holley war here, they're all good carbs and I would not hesitate to use any of them - and have done so as well as I still own all three brands.

Main thing with any of them is try to get an unmolested one - new would be preferred.
All of them come jetted abut 5% rich for the expected engine size they'll be used on.
Nice part about that is, you can get the car running and drive it while you work any other bugs out and then start the fine tuning bit.

Fwiw, The Carter and Edelbrock both come off the Weber assembly line and are the same carb.

I know that a lot of guys run Holley double pumpers on the street and do ok.
By the same token I see a lot of cars at the strip running double pumpers and they'd do better with a vacuum secondary Holley, but . . . since that ain't Official Hot Rod Drag Racing Stuff they stick with their ill-running double pumpers....