One more time on the noise blanker diodes...
The noise blanker detector typically uses unbiased germanium diodes. An unbiased germanium diode detector will still work reasonably well for tiny signals.
However, swapping these diodes for Schottky may well actually make the detector worse because Schottky diode detectors really do need to be slightly biased in order to become good low level detectors.
In reality (for a noise blanker detector) I suspect it would make little or no difference on car ignition interference either way anyway 
The NB detector is there to detect a large and sudden pulse of noise energy and it will blank the receiver (i.e. you don't hear any output) for a time period that is slightly fatter than the pulse of ignition noise from the car.
So you are actually listening to a soundtrack with tiny pulsed gaps in it that line up with the ignition events in the car.
In order for the noise blanker to be able to detect and capture the fast pulse of ignition noise 'quickly' it listens for large noise events over a bandwidth of several hundred kHz at the first IF in a typical Uniden CB. i.e. maybe across 20 or 30 channels.
This can't work with fuzzy hiss noise you hear on your chosen channel and there won't be 'louder' CB signals with this mod. Period.
As for the Schottky diode mod in the AM detector I am pretty much telling you it won't make any difference because the detector uses a forward bias current that is optimised for the 1N60 germanium diode.
If you swapped in Schottky diodes the bias current would still be pretty close to ideal but there wouldn't be any difference in signal to noise ratio as both detectors will have similar efficiency.
Note that if you put the Schottky diodes in a radio with an AM detector that used silicon diodes eg 1S2075 diodes then I would expect that the detector efficiency would become quite poor because the detector circuit would have a higher forward bias to suit the silicon diodes.
This would bias the Schottky diodes to a point well away from the ideal bias point and would kill the detector efficiency
If you rebiased the detector to suit the Schottky diodes then you may well make the detector perform better but you would also have to make sure the detector didn't then overdrive the audio stage after it.
In short, each AM detector circuit in the CB will be biased to suit the original diode type fitted and the load impedance and drive level from the detector will be chosen to match the diodes.
Just swapping the diodes might mean you make the radio worse.
