Is there a good mounting hole location in the bed of a dropside M35A2?

[Crit]

I'm looking to use someone else's M35A2 for some vibration testing that I need to do for work. I need to mount an accelerometer rigidly to the bed but still allow a load to be placed in the bed. Can anyone think of a good place to use, other than welding an adapter to the bed and grinding it off when I'm done? Is there a threaded hole or thru-hole somewhere on the bed's load surface on either the top side or readily accessible on the bottom? I'm also looking for a backup truck to be used for testing in case my current plan falls through for some reason.

 

[steelandcanvas]

Sometimes there are bed drain holes in the front corners, probably about 3/8" in diameter.

 

[donnerwetter58]

The dropside beds have two slots in the floor at the rear of the bed for the troop seat turnbuckles to engage in.