Mike, like you I also use 5052 for the aftermarket radiators I build here in Australia. I use 2mm sheet which would equate roughly to .080". I have used 5005 in the past with no problems, it's just a little softer than 5052 and can dent a little easier.
Weldablility on either 5052 or 5005 is excellent.
Another grade which can be used is 5251 which has similar properties to 5052 but is is quite rare.
For filler wire I prefer 5% magnesium (5356). It's a bit tougher than 5% silicon (4043) and if any welding work requires anodising it is the closest you can get to colour matching. (4043 and 4047) will anodise black regardless of anodising base colour.
I also like using a rod diameter of 1.6mm (.065") as I feel it gives a flatter and better looking weld than 2.4mm or larger. With this wire however, it does require a close fit with very little gaps.
Make sure you remove the furnace brazing from the weld area with a clean file as it gives the weld a very "drossy?" appearance.
Good luck with your radiators, it a part time thing for me but I enjoy doing them very much.
Regards Andrew.