Bench seat install advice

[General23cmp]

1972. What's the best way to get a newly covered bench seat into a nicely painted and ready cab? It just seems like a tight fit, and I don't want to open the door too wide and damage anything. Should the rails be attached to the bench prior to going in? Do they get attached to the floor or seat first? It seems like either way, there will be bolts that are almost impossible to reach. I assume the seat back and bottom go in attached since the upholstery wraps around that joint, and I assume doors are not removed (I don't want to do that).

Thanks.