The lengtrh of the seat pad is the same on both seats. However the Scheel-Mann thigh pad is separate and can be moved forward creating a deeper seat to relieve thigh pressure points.
The Scheel-Mann seat pad height from the seat bottom mounting plane is lower than the OEM seat.
The adapter brackets from Wedge Brackets in Utah should bring the Scheel-Mann seat uop to the same seat pad hight off the truck cab floor as the OEM seat.