Well, I took a shot at it. The dent came out pretty well, (still not quite 100% back to shape). I'm going to spend some more time tapping the smaller recesses back in shape, and then I need to refer to Keith's 'polishing trim' section and get some of Foggy's sanding/polishing materials on hand to get started polishing the grille and headlight doors.
Thanks to James72 and fordman for the tips - I used both of them... made a little wooden die, shaped like the profile of the area I needed, and clamped it in the vise for a backer; then cut off a broomstick handle to about 8" and used a hammer to tap the rounded end against the aluminum - that was very effective, and left much less hammer damage than using the hammer directly against the metal.
It definitely looks better (at least it's less noticeable)
Obviously, it's still not perfect - I'm no sheetmetal fab guy fersure... but I think with another couple hours of tinkering, I can smooth it out pretty well. I'll post more pix once I get there.
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'65 F100 Custom Cab Shortbed - current project
'69 F250 Ranger CS (Tug) - P/S, P/B, AC - 390/C6/D60 - Reef Aqua/Wimbledon White [sold]
'66 F100 Custom Cab (Shep) - 352/4sp/9" - Wimbledon White [gave to OldDawg]