My '93 5.0 Mustang seems to have a bad oil pressure sending unit. It moves around much more than it had in the past and I suspect it is going bad. I am considering replacing it with a mechanical oil pressure gauge. I would like like help in picking one out that will do a good job but is not too expensive. Anyone with insight on this ? Also, while on that subject, with 85K on my motor what average oil psi should I expect with the mechanical gauge ? Just ball park because I know there are alot of factors. Thanks for any help ! Mike