There are two types of pumps on 617's, perhaps correlated with NA and Turbo. I rebuilt my old style on the engine yesterday and the instructions sometimes posted here on how to rebuild a 617 vacuum pump from the Easley list definitely are for a different pump than mine.
You can tell the old style by a clear hose going from the pump to the air cleaner.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

There are so many restrictions, orfices, solenoids etc. that there is no good single spot to connect a vacuum gauge. Right at the pump might show that there is a problem but the locks not working or the tranny not shifting right might show up before you would see anything on the gauge.

__________________
Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

You are correct about that. I should have been clearer, there are not two interchangeable types of pumps on the 617, unlike the 603. There are many posts here about upgrading the 603 from the old to the new type pump. On the 617 you have no choice, you have to use the type of pump for your vintage engine. My 617 turbo (the one that failed) was the "new" type pump, without the exhaust line to the air cleaner. AFAIK, catastrophic pump failures are unusual on 617s.