Daniel, if you are considering making a horse box, then I would recommend a Luton, it's not as easy or as cheap as you think to convert on a DIY basis. I seriously suggest you look at as many conversions as possible and take photos for reference, my ate supplies vehicles to the horse box trade for conversions, but these are usually Iveco Cargos as they have sleeper cabs etc.
Carpentry skills will only play a small part in the conversion, engineering is the skill you will require mate, spring assisted ramps etc.
Don't forget, if you tip up in a Tranny van full of horses and it looks like a tranny van, the RSPCA will have a field day with you, and I recon VOSA may have something to say mate.
That's my bit mate, just trying to help.
