I would go with a current production Mark III. I like the FN roll stamp of their logo, so I'd choose it over the BAC since that is the only difference (other than possibly price).
If I was going to customise one, I'd look for a good used Mark III. I wouldn't concern myself with whether it was cast or forged. I honestly don't think it will matter for one iota.
If I was going to customise one, I'd look for a good used Mark III. I wouldn't concern myself with whether it was cast or forged. I honestly don't think it will matter for one iota.