1972 914. Found numbers "2749551" stamped in the lower right rear corner of the rear trunk floor. Do not match the VIN. What do they mean? Car been knotted together? Production #?

That's the chassis #, not going to match the VIN. Someone more expert than I will chime in but you can figure out date of mfg from that. So long as it's "in range" to the VIN production info and there's nothing else to indicate your car's been clipped, you're probably fine.
And I'm speaking from experience. I had a car that had an impossible chassis #: the vin was from '73, the chassis # from '74, and far enough apart to indicate the car was clipped.

Check the drivers door frame plate below the A pillar. And also I believe you'd find that number on the passenger side light bucket, there is a plate viewable opening the frunk.

www.914world.com/bbs2/sources/action_public/pop_helpchassis.html

Click to view attachment

Many thanks.
Confirmed the numbers in question with door plate and under dash scribble. Same.
Slight sigh...