The flat top coupes have the same room inside as the the sedans. The round top coupe have the same seat mounting points, its the round top that gives the driver no head room. So, the seat is then moved forward or laid down for head room then no leg room. I have long legs and I have a sedan with a 10 deg. seat. I had a 20 deg and it moved the seat bottem too far forward and me knees were hitting the wheel.
Now a 10 deg kerkey seat that is only about 18 inches from front to back, that is the shortest I have found, 1.5 inches longer steering shaft, and a 1.5 spacer on the wheel. With a full 3 inches longer steering shaft it was hard to get in and out.
My seat is on the floor and back flush with the rear "firewall"
These cars keep me in shape over the winter, one burger too many and I dont fit..LOL