SAE j518 standard pdf covers complete dimensional specifications for the flanged heads, hydraulic split flange clamp halves.
It is applicable to 4-bolt split flange type tube, pipe, and hose connections with appropriate references to the O-ring seals and attaching components used in their assembly.
Also included are recommended port dimensions and port design considerations.
SAE flange fittings and adapters , with the flanged heads specified are incorporated into fittings having suitable means for attachment to tubes, pipes, or hoses to provide connection ends.
The hydraulic flange fitting end connections are intended for application in hydraulic systems, on industrial and commercial products, where it is desired to avoid the use of threaded connections.
You will find this link, with your need standards.