the sensors work on the hall effect principle, basically they are rotating magnets with an arm on them. Disconnecting the battery will not make a difference to the setting.
Changing them should not effect the calibration too much....
Change them then let the system settle. Measure from the...
if it's done 72K it maybe still on the original belt, being an early 300 '1994' it may have the earlier crank timing pully. If the crank pulley has not got shoulders on it... change it for one with shoulders.
more likely to be a cracked bias plate than broken bias springs. bias plate has slightly oval holes, test drive the gear change before riveting it all back together as a little adjustment may make all the difference.
What I think you are experiencing is completley normal.
To test this:
grab a pencil a notebook and a tape measure and run outside for me to do a quick two minute test.
go out to the car and measure the distance from the centre of the wheel to the bottom of the wheel arch...
How often do you plan on doing this?
If thats all you want to do with it... then an longer lead to fit into the front cigar socket with your crock clips on it seems the simplest solution.
I have silicone hoses on my 300.... waste of money!
Although they look pretty and may not delaminate over time.
but if you think they will make a difference to performance, think again. this is a two tonne beast with the aerodynamics of a wardrobe.
Here's another one:
'Ware Hertfordshire 1963'
including footage of the very car that conqured Ben Nevis in 1963
'45 FWD'
the Land Rover Club, Original rare Vintage Series 1 footage: 'Ware Trial' Hertfordshire c1964 - YouTube