What code is the system designed to? As an example B31.3 doesn't include B16.38 valves in its "Component Standards" but other codes might. This isn't a comment on whether or not it can be used per that code. Clarify what the system is designed to and that might explain if a B16.34 valve is a replacement for a B16.38 one as a reasonable replacement.
Thanks,
Ehzin