It is standard practice for engine assembly to lubricate items such as bearings, piston rings etc. with engine oil. The Briggs manual says oil seals are to be lubricated with engine oil before assembly, but I can't find a direct instruction for what to put on the bearings and rings, so I use engine oil as always. Remember, whatever you use stays in the engine in service, so it has to be suitable for that purpose.
If you are talking about assembling items that require the use of a press, special lubricants may be advantageous.
