@Stan Galat my car is the IM roadster, it’s a tube frame. I just bought the seats from VMC is all. I got some great input here. Car comes back to me today I’m excited to mess woth all the options. I’ll most likely go fixed position on the floor. In the rare instance someone has to drive it and they can’t reach the pedals, a pillow will do!
I'm so sorry for misunderstanding. If you've got a tube-frame IM, you have a lot of possibilities.
The cheapest option (by far) that looks "right" in a Roadster is the EMPI 62-2960 - they look a lot like Henry's Roadster seats, or a Procar 90 series. Mounted directly to seat sliders, they ride higher than you'd like, but still sit pretty low for a spring seat.
I have a set in my car (my third set of seats in search of something that would satisfy my wife and I both) - her's is unmodified (other than being recovered in leather), mine is heavily modified to sit very, very low in the car, and still use sliders. I completely remade the bottom frame of my seat to actually recess the tracks into the frame, and cut down the cushion. Upholstery was not easy and not cheap, but I made both seats match. and feel good to both Jeanie and me.
Both seat bases are pitched back aggressively, but if you look at the base of mine, and compare it to the base of hers, you can see what I did.
What I had said in another thread (about a year ago) was this:
"The passenger's seat is "as delivered", with a set of seat sliders bolted to the bottom. It sits surprisingly low for a spring seat.
My seat (however) is so low that I recessed a track into the cushion on either side of the center section (in the bolsters) so that the bottom of the springs in the back of the base are flush with the floor, but the seat slider remains functional. The back support grazes (well.. maybe "drags" is a better word) the carpet when the seat is all the way back, but the sliders are on an angle so that the seat rises as it moves forward. The springs are all there, which makes an enormous difference in comfort.
I cut down the foam in the seat bottom so that it was about 3/4 of an inch thick at the junction of the seat and seat-back, and tapered it upward towards the front (which was left intact. I had to buy a 18" long serrated knife on Amazon to get a nice cut. The upholstery shop had to add 2" of foam to the bottom of the seat-back to close the gap created when I cut the cushion down.
My butt is about an inch and a half (or less) off the floor in my normal driving position. I was able to get as low as I was with Fibersteel seat shells, mounted directly to the floor. I also pitched the seat base pretty aggressively, as pitching back makes an enormous difference for me being comfortable. The recline adjustment on the seat-back allows me to fine tune the fit depending on if the driving is aggressive or interstate.
My wife (5'5" ish) sits like a very small child or a 90 year old woman in the driver's seat. The top of the wheel is roughly even with her forehead."
The takeaway of the last paragraph is that remaking the driver's seat so that it could slide was probably just an exercise in proving I could, rather than doing anything useful. Bolting an unmodified (but tipped) 62-2960 seat to the floor would have provided 90% of the comfort at 10% of the cost.
I have more details (but not as many as I thought) on a thread I started to detail my 2019/2020 winter projects. The link is here, and the seat part of the program is on Page 4.