Power Steering pump type/configuration question.

[Xbird]

Have a '78 Jamboree, MB400 chassis. Running into belt squeal under load, usually right around 62 mph and i have to drop back to about 45 to get through it then feather foot back up to speed if I'm lucky, otherwise I'm stuck witha  squealing 48 mph speed limiter ... yes I've become "That guy" on the highway 

In checking through things, the pump looks more like a gm trapezoidal shape that im used to than the older "oblong neck on a round can style" as shown in the '78 chassis manual.

Running a single belt, that i've replaced and cleaned up the pulleys. My first road trip with it, the issue was much worse. A roadside inspection session revealed that the single belt was running on the wrong pulley groove and very misaligned. Fixed that and it runs now as described above.

There is still a bit of misalignment that I can see. so the pump and mounts will be coming off to be spaced out about 1/4 inch. During previous owner's time, an engine rebuild allegedly occurred, so there is the chance that some spacers were lost. 

My  main thought has been that since it is such a longish belt run, and the crank and idler pulley are two-groove jobs, did the thing originally have a two groove pulley/pump that might have been replaced. The manual only shows a single groove pulley with the skinny belt Any input appreciated.

[DaveVA78Chieftain]

Far as I know, the 440-3 fan belt set up in a MB400 Class C van chassis with AC is the same as the 440-3 in a Class A chassis with AC

[Xbird]

Thank you, what i have is essentially the same as in your pics, nicely done engine resto btw.

Only main difference is the pump type and also pulley diameter on mine is smaller. otherwise routing etc is all the same. Hoping that correcting the misalignment, another emery cloth go round on the pulleys and another new belt will cure it. my only other thought --but seems unlikely--is that it may be coming from the alt belts, there is a bit of size mismatch between the two that are are on it, one looks brand new, the other pretty well worn. No squeal at idle or slow speed turning, really seems keyed to engine rpm and acceleration load.

[Rickf1985]

If the belt has been slipping that much and that long then I can guarantee that the pulley itself is worn to the point that the belt is never going to seat in it correctly. You need to get a new pulley. It may look like if fits but it does not have the right contour to the grooves anymore.