The electro-vac is a electric vacuum pump for the wipers made by trico. Brad on here said they were a dealer option (50$) and usually only put on 3600's that were going to do heavy hauling up mts, hills since you wouldnt have any vacuum to run the wipers. I will probably end up just filling the dash holes and going with a hidden radio if I cant figure out what one this had in it. For the heater i'll try and get some more pictures tomorrow. It has this control panel on the left of the steering wheel under the dash, the bottom knob was gone and the middle one disintegrated when I touched it.

http://i138.photobucket.com/albums/q268/cotsi95/chevy%203100/heater.jpg

http://i138.photobucket.com/albums/q268/cotsi95/chevy%203100/2623c7f3.jpg

http://i138.photobucket.com/albums/q268/cotsi95/chevy%203100/f4e9502f.jpg

as you can see it doesnt have the warmer turn knob it has it on the panel on the left.

52' Chevy 3100 5 window