Holley fuel pressure regulators - High or Low ?

[powerband]

Clarification and suggestions for use with mechanical (stock) FP and tri-power carb setup. (Holley 1904's). I had a Mr. Gasket adjustable , worked but eventually diaphragm leaked, not going there again.

Both Holley items seem low pressure, I thought there were only FI(high) or non-FI (low), what's the diff' ?

(Summit vendor) :

12-803 - High-Pressure Fuel Regulator (std. finish)
---------- 4-1/2 to 9 PSI ---- 3/8” NPT Ports .220” (7/32”)

12-804 - Low-Pressure Fuel Regulator (std. finish)
------------ 1 to 4 PSI ---- 3/8” NPT Ports

Thanks

Mr (leaky) Gasket:

 

[FalconSedanDelivery]

Use the Low , in reality they are the same with a different spring inside , and if and when u need to rebuild it comes with both ( as they are exposed to air and can rust )