Regarding the distributor---look closely at the distributor vacuum unit--follow the path of the arm to determine which way it pulls the breaker plate. Many Volvo distributors have a vacuum retard-not advance. If you determine yours to be a retard unit you can go ahead and leave the vacuum hose off (plug the hose or cap the manifold fitting).
The spring loaded weights below the breaker plate control the action of the distributor cam and rotor--advancing timing with increased rpm. The cam and rotor part of the overall shaft can get gummed up where it fits over the lower half. It can all come apart for cleaning.
If you remove the lower drive take note of its orientation relative to the rotor--the drive is offset but can be installed 180 degrees off. -- Dave