Weird Seat Track Bolts

[richs]

Hello,
The seat track on my '58 bench seat is held to the
seat frame with bolts that have a very weirdly
shaped indentation. It looks like sort of like
a bow tie but has rounded edges. Probably done
for easy assembly in the plant? A torx
socket will work on some of the bolts, but strips
others. My next thought is to tack weld a standard
hex bolt to these and try to back them out that way,
then replace with standard hex bolts.

Someone smarter than me might have thought of
a better way to get these weird bolts out without
ruining them? Appreciate any suggestions.

Thanks