Grips, yes. I have no idea about Buckmark grips, but do think I could mold/carve an option for the 1911. I had a Delta Elite before the ban, and that was similar to the 1911 I believe.
Conversions - this is a can of worms.... If a gun is imported as section 5 it cannot be converted to section 1. It can be imported as parts, and if not assembled prior to modification could be built as a section 1. However, we spoke with a manufacturer back in the day, and they had local laws which meant they had to declare/register all gun types they made, so the parts are controlled and so on...
A Buckmark Section 1 rifle is a derivation of the pistol - with some extra wood bolted on, and a longer barrel. So if you took a Buckmark rifle, and cut the barrel to 300mm it would still be a rifle. If you then replaced the foot long stock with a foot long rod.... is it now a pistol or a rifle....?
It seems a mockery that there is no definition of a pistol/handgun, and that a cartridge gun must have a barrel of 12" and an over all length of 24", and then to distinguish between pistols and rifles for licensing purposes when they conform to the same rules on dimensions.