Should I overhaul my standard

Bought it with low oil pressure thought is was the
gauge put a new gauge on with 0-30 psi only
showing 5 psi when hot at idle and 15 psi when hot
at 1800 rpm can't afford a overhaul kit runs nice you
notice any knocks in video
https://youtu.be/qN0Gb7xPPm8

5 PSI means your real close to needing an overhaul before it goes ka-flooey. Curious now is a compression check of the cylnders, warm, throttle wide open, all plugs out, crank engine same amount of time for each cylinder.
Your oil pressure is determined primarily by bearing clearance. A new set of bearings might buy you some more time. Figure a bunch of labor and a hundred bucks. That should be a good band-aid fix for now.
Now you just wanna cheat the clock. 15/40 heavy duty oil is another option. If your already on 15/40 and 5 PSI hot, that bearing kit might be closer than you think.

link for video
Untitled URL Link

It doesn't sound bad to my failing ears .
Before you commit to an overhaul I would try a few things that should help .
Firstly adjust the oil pressure bypass screw at the top of the oil filter , typically these were set at the factory with eight threads showing above the lock nut and have never been adjusted since . Loosen the lock nut and wind the screw down to about four threads then lock down and check the pressure after a few minutes .
Your new gauge is only as good as the pipe supplying it , remove the pipe and clear it with a bicycle cable and compressed air followed by petrol , make sure the holes in the banjo fitting's bolt are clear as well .
If you haven't already , remove the oil pump screen from the side of the sump and make sure it is clean .
While you are there you might be tempted to remove the sump and change the oil pump , they cost seventy odd dollars and are easy to swap .

http://www.ebay.com.au/itm/Tractor-Oil-Pump-Gear-Set-Spindle-Rotor-Massey-Ferguson-TE20-TEA20-TED20-Fergy-/221823893142?hash=item33a5bbfe96:g:ILkAAOSwPcVVoZZM

Finally using 20W50 motor oil will certainly help an older engine and unless you live where it gets really cold it shouldn't affect performance [ bear in mind I live in sunny Australia ]

Depends on how much you use it. Could last for a long time. Don't sound that bad.

I have 2 87mm standards and both have low pressure when hot.I adjusted one to the point it sprung the gauge and now reads 60 lbs when not running. My thought is if my pump puts out enough cold to spring the gauge then my problem is elsewhere. I've read where missing parts such as o rings in the oil filter canister can cause low pressure. I think the manual mentions this.

How do I get to the oil sump

How to get to oil sump is it that side inspection plate
on oil pan

This is an FE35 with Standard engine sump , much the same thing as yours . The oval plate has a filter screen attached to it . Sometimes the studs come out with the nuts , this is no problem , just reassemble with lock tight and a new gasket . The oil pick up for the pump is also visible .

A close up of the pump body

I put 20w50 in here awesome pressure now but the
old girl don't wanna start now back firing farting and
running on a couple cylinders

I don't think that the oil change will have caused that . Good advice given on here is to look at each problem by itself without changing too many things at once . Otherwise you can get awfully confused .
Farting and refusing to start or running on three might be plugs or fuel .
If you are getting 20 PSI by cranking then there can't be too much wrong with the engine , even with heavier oil .
Did you adjust the oil pressure regulator screw ? [ marked B in the photo above ]