electric inline fuel pumps??

I have the Holley(Mr. Gasket is the same) Mighty Mite,Jegs part # 510-12-426.
Installed it on my 79 Chrysler with a 360 Thermoquad.The mechanical will pull thru with out any problem.At first I just wanted it for a primer but for fun I removed the mechanical pump to see if it would run and keep up with the engine needs.
It did,no problem.Tested it for 100 miles then reinstalled the mechanical and just used it as a primer. The above part # is for the 1.5 to 4 psi.I now have the #510-12-427 pump that is a 4to7 psi and is rated up to 400 hp on my 63 Belvedere with a worked 318.It too is used as a primer and I'll click it on if I get to run it thru the gears. Not a bad tiny pump for about $50.Also it can be barely heard with the engine running going down the road.