1929 plymouth u. How do you remove the back of the front seat? Was the upholstery finished after the frame was mounted?

You have to remove the upolstery panels nailed on the side piller above the seat.  There will be four screws to remove on each side.

So no bolts for the bottom of the seat?

Correct, no bolts hold the bottom, but there are two bolt heads in the floor boards that fit into recessed holes along the bottom of the seat back on each end.

Kinda like an old keyhole shape it slides in? But all I need is the top 8 bolts removed and the bottom slides back or forward to remove?

The bottom of the front seat is easy to remove by pulling up at the forward top and sliding towards the firewall.  The seat frame is held in place by fixtures on the floor that fit into the holes in the frame.  Removing the back of the front set is a bit more involved.

Sorry, miscommunication, I got the bottom of the seat off, just working on the seatback, I removed that panel and found the bolts in the b pillar, is there something holding the bottom on?

Ok.  As you can see, I needed to make a new bottom piece, which was done many years ago.  (I made new side wood this year)  No recollection of what original looked like or if there was enough left to determine much.  In the red circle is a notch, both sides, that are over bolts.  With the screws out of the B pillars, mine just tilted back.  It comes out as a unit, springs and side bolsters - I'll call them, no need to remove any upholstery.  It is unwieldy.  I had to lift the front end off the floor a little to back it out towards the back seat.  If you have rear flooring material, it may try to scrape along it and may make life more difficult.

Others may be able to provide better directions.

Good luck, you'll get it!

Thanks a lot

Bottom line, the front seat back is a very snug fit.  After the eight screws are removed, it will appear to not move. You have to work with it, try tilting it back, then lifting it out.  It is pretty heavy.

It must be removed to uploster it.

thank you