Thanks for the replies.
406 - I actually went to Simpson's site just after I posted this and saw their mounting recommendations and read about the 40 degree angle requirement. This must be somewhat recient because I had a set in my '65 Mustang that mounted to the floor but that was back in the mid '80's.
cdowns - the truck is a project that we bought and are putting together so I haven't heard it run yet, but it seems to be a semi-hot 350 with an eaton 4.10 posi, so I may have to mount a wood block to the floor.
