Alon Vacuum system

Does anyone have any information on servicing an original Alon A2 vacuum system.

I have been toying with the idea of upgrading the original DG and AI in my Alon to something newer (1980's at least), and also servicing the vacuum system as my system pressure is showing only 4.3 inHg. 
The existing system seems to be a "closed system" as in no way to replace air filters etc.
I haven't been able to find any parts on the Univair site either.

I have included some pictures, so if anyone can identify the parts and possibly give me some guidance on servicing this system I would greatly appreciate it.
Also, I have considered EFIS products like the Garmin G5, but have decided that for my purposes they would be overkill. I am just looking to upgrade to more modern vacuum instruments.
Thanks everyone.
Martin