Hi Dan;Don't fret.  This is not a problem.  Not surprising that the bolts from your OEM bumper don't fit, its flat, as opposed to your nice new tube bumper.  If someone does not come up with the exact answer, measure the bolt hole (verniers would be nice, but a good eye and a ruler will work), estimate/measute the distance from where the bolt head goes to where it exits the frame.  Add washer (2) and nut length and a bit more.  Go to wherever you get hardware, buy the bolt and try it.  Don't be disappointed if it takes a couple of tries.  Usually hardware places don't have a problem switching incorrect bolts.  Hardness shouldn't be an issue, unless someone else chime in on that.
Dave B.

-----Original Message-----
From: Dan N <dn92610@GMAIL.COM>
To: vanagon <vanagon@GERRY.VANAGON.COM>
Sent: Wed, Oct 3, 2018 1:56 pm
Subject: please help - bumper bolt

hi all,

does anyone has this steel tube style bumper? if you do could you please
tell me what size of the bolts?

the pics of bumper and a bolt - the bolt is from OEM square style metal
bumper and it doesn't fit in the tube bumper. The OEM bolt is a bit larger
in diameter and has different thread.

https://www.thesamba.com/vw/forum/album_page.php?pic_id=1829844

https://www.thesamba.com/vw/forum/album_page.php?pic_id=1829845

thanks

dan