97 Ram 2500 dsl 4500 trans has a vent or vacuum line attached at rear. where does it attach to at engine area?

SOURCE: Vacuum Line Schematics

There are MANY sites with information as well as diagrams available created specifically for select areas of Vehicle maintenance. --NO sarcasm intended or implied--
Use Google or your preferred search engine and type in your Vehicle and you should receive a Phone Book of options.
Vacuum Lines are generally the same on the same Make of Automobile except of course for differing Engine sizes and years of Production, otherwise ask the person or persons that did the partial rebuild.

This is the way (Google) I usually discover what I'm seeking.

SOURCE: 97 dodge 2500 4x4 will not engage

On the axle there is a vacuum Actuator that engages a collar on the axle that engages the four wheel drive if the axel splines are worn or havent been lined up they will get burred and won't allow the collar to line up. You can remove the actuator and see the splines and determine if they need to be fixed.

SOURCE: Dodge Ram 2500 engine ping

Your ignition timing may have advanced too far. Or it is now where it should be and is making more cylinder pressure during combustion causing the gasoline to ignite to early causing detonation or ping.

Make sure the ignition timing is correct. If it is try better fuel meaning the octane rating.

If you can go up to the next octane level. For example if you are using 87 go to 89 and see if it goes away. 3 of my wife's last cars a 1986 Honda Prelude, 2000 Neon, and a 2003 Neon had some ping under medium to hard acceleration. She switched to 89 octane and the ping went away completely in each vehicle. Each of the vehicle had a good deal of miles on them.

The 2003 Neon has 75000 miles on it now and runs great on 89 octane. About a year ago I tried 87 Octane in her car and the ping came right back.

SOURCE: fuel pressure regulator had no vacuum line connected

another engineers wet dream. think of it this way . what is normally in the intake when the engine is running.. answer vacume, hence the regulator gets its vacume without a hose connected to it as its already in a full time vacume chamber.no hose required . ps be carefull to seat the regulator and o rings securely into the housing befor you reattach the secureing metal clip.
good luck chris

SOURCE: diagram of vacuum lines

I think this is what you are looking for.