You would have to look for a base model car ,probably 6 cylinder, that had the power option delete package on it or find one for sale after market.
AGR comes to mind.
My dad has a 69 six cyl. car that came with manual steering.It's a truck in a parking lot but once up to speed it is ok.Don't know if you would enjoy that on an every day driver.
The '69s were rear steer and the '70s are front steer.A quick check of the Hollander Interchange Manual would tell you if the 69 manual box would work at all.Frame mount pattern and pitman arm being the critical parts dimensions to watch for .
Also ,don't know what year it changed,the splined stub shaft (input) of the later model boxes is a smaller diameter than on the earlier ones.
If you are putting an earlier style steering box in a later model car the "rag joint" coupler splines will not match up.
I'm putting a WS6 box from an '81 into a '70(mounting bolt pattern and pittman arm are the same ).The diameter of the rag joint splined female coupler from the'70 coupler is to big to fit the '81 box input shaft . This requires getting the proper dia. coupler for the later model steering box for the year car the box came out of.If you are putting an early box in a later model car the input shaft will be too big for the late model coupler to fit over it.
The hydraulic fittings coming out of the late model boxes are different too(not sure when this changed) .They use an O ring seal as opposed to the SAE inverted flare fittings on the earlier cars.Why they changed was probably a cost cutting measure?
The nuts will thread up but the flares won't seal properly to the newer style PS box female inlet and outlet recievers.
The WS 6 box is desireable if you want qiuck ratio steering ,Three turns lock to lock, but can get you into trouble if you have a poor handling car.
My neighbor used to race dirt track stocks and they used to take the p.s. boxes to a guy and get them converted to m.s. .
Check with some of the dirt track or circle track guys in your area and see if the are converting the PS boxes to manual.