[hatzie]

This has been discussed earlier in this thread across several posts but I'll rehash it in one post.

You can't use the 81-86 switch on a TBI truck because the 81-86 switch is momentary. When you remove your finger from the switch the selected fuel pump will shut off.

You can and probably should use the TBI tank switch on all of them.

There's a bubble in one of the male switch terminals that mates with a keying notch in the plugs. This prevents swapping the TBI switch with the earlier 81-86 switch like you tried to do without modifying the connector to add an additional notch.
The converse is also true. You have to notch the 81-86 and diesel plug to use the TBI switch.

Open up the 1991 wiring diagrams and go to pages A80 & A81

The plug terminals in the Diesel and 81-86 gasoline models are on the centre switch terminals with the ground on the LEFT and Hot on the RIGHT.
The TBI plug terminals are on the outer switch terminals diagonally positioned with the ground on the RIGHT and Hot on the LEFT.

The valve motor power wires on the dash switch are rotated right to left and up & down in the same manner so the polarity across the switch to the valve motor in the RH & LH switch positions ends up exactly the same.