Focus is not the issue here. The issue is coverage.

Any lens gathers light from a cone in front of it (angle depending on the focal length), and projects it to a cone behind it (angle depending on coverage). So long as the lens is far enough away from the film plane, there exists some plane in the real world that will be focused on the film plane.

But...in the case of your SMEMA lens, designed for 35mm format photography, focused at infinity, the projection cone will end up covering approximately a 22mm radius circle. To cover the full 8x10 format, you would need coverage of at least 180mm (both calcs, see Pythagoras).

Also, being a 40mm lens, the lens would have to be placed 40mm (approx, from focal centre point) from the film plane. If you look at how your camera is setup, you'll see that it is expecting lenses to be mounted approximately 200mm away.

You could mount the lens further away, and as the light projected is a cone, it would cover more of the film. Huzzah! Oh, but that would then mean the focus getting closer and closer into the extreme macro. Napkin calculations. at 400mm extension the lens would have enough coverage. At that distance, the magnification ratio would be about 10:1, and the focal distance might be closer than the design of the lens would allow. Oh, and you'd need to dial in 7 stops of exposure compensation at that extension (more coverage implies less light per unit area), so good luck focusing on the ground glass.

No shortcuts here, I'm afraid. Larger format cameras require lenses with sufficient coverage. Yes, copal shutters at this size are expensive. For a cheaper alternative you could use in conjunction with your Soviet glass, trying searching for a 'Thornton Pickard' shutter that can be situated behind the lens.