Unhooking wont hurt anything, except the Oil pressure sender/switch.
That turns the fuel pump on after oil pressure is established, it also has the circuit for the dash gauge in it.
The sender/switch is at the back of the intake , but you can put the line for the mechanical gauge in a different location. Down on the side of the block next to the oil filter may be a port that you can use, and leave the electric gauge hooked up as well.
Also, the coolant sensor for the TBI is next to the thermostat housing, and you dont want to remove that one.
The temp sender for the temp gauge, should be in the side of the cylinder head, on the drivrs side. Look for the sender and the hole it is in. There may be a hole on the opposite cylinder head that you can use( just remove the plug) for the mechanical gauge and also leave the electric coolant gauge hooked up.
Hope this helps
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