I have had great success with PCem (http://pcem-emulator.co.uk/)

Config:
gameblaster = 0
gus = 0
ssi2001 = 0
voodoo = 0
model = 39
cpu_manufacturer = 0
cpu = 27
cpu_use_dynarec = 1
cpu_waitstates = 0
gfxcard = 15
video_speed = 5
sndcard = 0
cpu_speed = 21
has_fpu = 1
disc_a = Z:\Users\<redacted>\id.ima
disc_b =
mem_size = 262144
cdrom_drive = 200
cdrom_enabled = 1
cdrom_channel = 1
cdrom_path = Z:\Users\<redacted>\SCO-2.1-CD.iso
vid_resize = 0
vid_api = 1
video_fullscreen_scale = 0
video_fullscreen_first = 1
hdc_sectors = 63
hdc_heads = 16
hdc_cylinders = 511
hdc_fn = sco-testing.img
hdd_sectors = 0
hdd_heads = 0
hdd_cylinders = 0
hdd_fn =
hde_sectors = 0
hde_heads = 0
hde_cylinders = 0
hde_fn =
hdf_sectors = 0
hdf_heads = 0
hdf_cylinders = 0
hdf_fn =
drive_a_type = 5
drive_b_type = 7
window_w = 0
window_h = 0
window_x = 0
window_y = 0
window_remember = 0
joystick_type = 0
mouse_type = 0
enable_sync = 1

[Joysticks]
joystick_0_nr = 0
joystick_1_nr = 0

cdrom_channel MUST be 1, and the floppy MUST end with an extension of .ima

It runs on windows and linux, and happily in wine in macos. Once the install completes I am confident it will work on bochs et al:
file sco-testing.img
sco-testing.img: DOS/MBR boot sector; partition 4 : ID=0x63, active, start-CHS (0x0,1,1), end-CHS (0xfe,31,63), startsector 63, 514017 sectors

It's not a special image format, but a raw image.
--
  Cory Smelosky
  b4@gewt.net