Hi John

I think the measurements you want are here:

https://chevy.oldcarmanualproject.com/chevyresto/52125.html

but they are very hard to read.

I think the highest part of the seat cushion is 14-1/4 inches above the floor (your measurement 1).

The second measurement you want isn't given, but a measurement from the lower front of the back rest to the front of the seat cushion is.

Problem is, I can't read what is is for sure.  But I think it's 18-1/2 inches.

What is easier to read is that it is 27-7/8 plus 17-1/4 (45-1/8 inches) from the front of the dash to the lower front of the back rest.

Hope that's what you were looking for.

@ole-olson thanks very much. Your dimensions will help my neighbour have a new seat built. He will probably join our club soon as he finds more fun!  John