I unbolted the heads from the bases on both my original mirrors & the MUTH MIRRORS and swapped them. The MUTH's has an adapter on the main pigtail that has the leads for the heater connected to it so I would have had to drastically change out the ends of my in-door harness from a 4-way connector to an 8 way connector like on the end of the MUTH's. But I discovered a different way to do it.
The '92-'98 mounts...
My original mirrors with the mounts removed....
And the MUTH's with my original mounts attached to them....
In this picture you can see the connector for the power mirror at the bottom of the pic and where it plugs into the adaptor with the 2 leads for the heater.
I cut the heater leads from the adaptor and added the same type of connector to them as what is on the leads for the turn signals as shown in these next 2 pics.
Red/Black wires with white connector = turn signals
Black sheath with 4 leads going to black female connector = power mirror
Double Black leads to white female connector = mirror defroster
So far, I've got the P/S mirror mounted up on the 'burb and the extra wires routed through the boot and the grommet in the P/S sheet metal under the dash.
In order to get the wires through the grommet, I cut an old wire hanger and made a "fishing tool" out of it. I doubled over the end of it and shoved it through the grommet, threaded the leads through the loop one at a time and while holding the grommet with my right hand I pulled the wires through with the fishing tool.
