Ok guys my brothers truck has the 2.9L it is a 1990 Ranger with a 2.9L auto it is a good truck but not as good as my 1991 with the 4.0L. Well nayways to the point, he is slowly losing oil pressure(over the past year) and we are wondering what it may be I am thinking that the main bearings on the crank are bad but he seems to think that his oil pump is failing the truck only has 52,000 miles on it but sat for about a year any thoughts that might help me out on this before I take the motor out and tear it apart, my thought is to just swap a 4.0L in it if I don't feel like fixing it.

he is slowly losing oil pressure(over the past year)
According to what? the POS idiot "light" that pretends to be a gauge in the stock dash? Or do you have an actual (mechanical) gauge on there?

If the engine does infact have problems, then yeah, I probably would go for a 4.0L instead of rebuilding the 2.9. The extra torque is nice to have.

Yeah it is the stupid original gauge I should probably just get an afermarket oil pressure gauge for it I know the stock one really does nothing but it may also be working the way it should