Take the back seat out and called it a commercial vehicle. Plenty of dealers did that in the mid 80's to enable their customers to dodge new car sales tax.
One of the other dads at our children's school has, or at least had, a Triumph 3500 with a holley carb on it and he reckoned it hogged the juice something horrendous.
Is the radiator overflow bottle from the GA15DE going to become surplus to your requirements? The one on my youngest's Pulsar is cracked and has a hole in it.