Believe it or not I haven't the ability to post an image, at least for now. No doubt you're correct. The rest of the machine is is such good condition, I feel confident that it's never been outdoors for any significant amount of time. I'm not doing a "Ground up" restoration because it's in such good condition but the rust hole does throw a bit of a wrench in my plans.
Now to sort out as good a patch as can be mustered without removing the liner,..... (again I'm open to suggestions)
Thanks for the reply.
If it is just an enlarge evap' coil mounting hole that would have secured the corner flange of the front left side of the coil housing to the floor of the liner/tank, you may be able to use a rubber/expanding "well-nut" which will do two things for our situation, 1st it will fill & secure the rusted out hole, 2nd it will provide you with a means to secure the evap' coils mounting screw back to the floor of the liner without removing the liner.
But there are limits to the diameter that the "well-nut" can handle, typically the size in diameter of an American 5-cent/nickel coin. you can find them ( well-nuts) at Lowes or Home Depot stores in the hardware drawers down in the hardware isle, sometime they are referred to as rubber / expanding nuts. here's quick Google search result....http://www.google.com/#q=well+nuts&hl=en&safe=off&prmd=imvns&source=univ&tbm=shop&tbo=u&sa=X&ei=2ui-T5bJHNOEsAKj2InNCQ&sqi=2&ved=0CLQBEK0E&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=1429de5fade86fa3&biw=983&bih=494