Hmm. Barrel lenses? Which barrel lenses? In particular, what focal lengths and maximum apertures?
I ask because I've had some success with barrel lenses mounted in front of a leaf shutter on my little Century Graphic. The shortest is a 60/14 Perigraphe stuffed into the front of a mutilated Ilex Universal #3 (top speed, and it is accurate, 1/100). Longer lenses in front of a Copal #1. I mention this not to recommend a Century Graphic but to point out that front-mounting is possible with lenses that aren't retrofocus.
Shooting hand-held with guess focus and guess framing limits you to fairly short lenses, no movements. Think again about how you want to use your proposed camera.
If you must have a focal plane shutter, you want an unmutilated Pacemaker 2x3 Speed Graphic. The frame finder and tubular view finder (with appropriate mask) work better than guess framing. The shortest lens I have in shutter that will make infinity on it is a 58/5.6 Grandagon (not retrofocus). It is in shutter. The shortest barrel lens lens I have that will make infinity on it is a 1.75"/2.8 Elcan (retrofocus) just covers 6x6; you're probably not going to find one of them at a reasonable price. If you must have one, 180633060975 has been on offer for months.
make me think you intend to use a retrofocus lens from a 6x6 SLR. Bad idea on 2x3 because of limited coverage.(in case I use a really deep wide-angle or something)
If you must have movements, make an imitation 2x3 Galvin, focus on the GG, shoot from tripod, and use front-mounted lenses when you can't get a lens in shutter that will do. Or just get a Galvin, they turn up ...