Really Dirty Engine?

Can't add a thing to that,....Only repeat....leave that sleeping dog lie,...............

Happy Roddin' 4TTRUK

 

Wake their *** up! You have to work in the morning.

 

That's pretty typical of engines from that era that didn't often get driven long enough to get warmed up real good and may not have had the oil and filter changed often enough.
As someone mentioned above the "road draft" tube didn't (and doesn't) work very well when the vehicle isn't at actual highway speed where the air going past the end of the tube creates a venturi effect and draws the fumes out of the crankcase. The rest of the time sludge happens because there isn't enough air flowing p*** the end of the tube to ventilate the engine. Remember that guys changed the oil every thousand miles for a reason in those days and it wasn't the quality of the oil at the time.
You can most likely get away with just changing the oil and filter on an extremely regular basis for a while but If I wasn't planning on doing a full rebuild on it any time soon and planned to put some road miles on it next summer I'd pull the intake and pan and clean as much of that crud out as I could. A few hours time and a few dollars might go a long way towards keeping the engine alive on one of those out of town road trips next summer and help eliminate a ruined engine and ruined weekend.
Also if you are going to keep the damned road draft tube clean the thing and it's screen up in the engine out so it can breath as it is probably plugged up.

 

The motor in my wagon sounded good at idle but could only go a couple miles before the oil light would come on and the lifters started ticking,if you only do one thing it should be cleaning out the pan.