The part numbers:
$73.00 Napa Auto Parts: Part #: PS 385236
$47.00 BBB Industries 7350110; also part number 6337
$47.00 Vision/OE 7350110; also part number 6337
$76.99 Master Pro power steering 735-0110
Well I have concluded my research and found what appears to be a proper match to the 20,000 series SZ car pump! It is available from many sources under different part numbers depending on the brand. Some numbers listed above.
If your store doesn't have those brands, simply ask for a pump for a 1983 Buick Regal 4.3L v-6 Diesel. Also offer the part numbers, as often they have interchange part numbers in their computer.
This gets you a pump Identical to the Spur unit with same casting number on the case, same input and output locations and sizes. The pump is used on several large cars and trucks with large tyres, so it should have the required pressure and flow rate to power the steering in the Spur.
This saves $400-$800 off the price of a "RR" part, which has always been a GM part anyhow, and is very likely exactly the same unit. While I have not bought one yet to put a caliper on the shaft diameter to measure it, it does look correct. I figured out through research that the shaft diameters on these GM Saginaw type 2 of pumps are all metric. Either 17mm or 19mm. That is pretty easy to tell by looking at the photo. Photos of units with the fatter 19mm shaft look quite different than the 17mm.
This pump is the best match I can find and is superior to others mentioned above which are either for smaller cars or have the return port in a different orientation.
This pump was also used in some 1980s Jeep Wagoneer and Commanche models.
Beware that rockauto site also lists a couple of Lares branded pumps but the photos show the wrong style pump, those are the older type with the reservoir attached, which won't fit a 20k series RR. Always make sure the photo of whatever pump you get shows the (small GM type ii) pump without the reservoir.
Cheers everyone. Maybe an update could be made to put this last post first, so folks don't need to read all the prior posts. I had put them up hoping someone else would have the answer, so I could send a pump to my family who busted theirs on a road trip.
Similar amounts of money can be saved by purchasing an a/c compressor directly from the Sanden website. Sanden made the compressor for the SZ, and most parts sellers don't sell genuine Sanden units, but rather, Chinese copies, which don't last long and spew metal shavings into your whole system.
Sanden don't make the model 510 anymore, but they make a later 7 piston model which is what RR specify. The Sanden numbers are
Type: Sd 709
Model Number 7641
That's $249 direct from Sanden website.
For enhanced cooling, Sanden make a special unit with 15% more capacity, which I recommend especially if using 134a refrigerant. The enhanced model is $319 from Sanden direct, part number 4616.
RR specialists and parts stores alike will sell you chinese copy with their house brand on it. I didn't have this info and bought a compressor from Albers for $550, which was their cheapest reproduction unit they get from Introcar. I couldn't stomach the $1200 price for the genuine unit from Albers which is a real Sanden unit in a stylish Bentley box. The repro unit that I got, I could have bought for about $149 if I had known the part number. I will end up doing that job over again with the genuine unit direct from Sanden. Maybe I will make a new thread with the Sanden info.
Use your PMC for mental therapy. I replaced my psychiatrist with a PMC. Thirty minutes of driving per day is more effective than doctors and drugs.