John,
Don't know if it is of any interest but if you do go with the 318 I have a "Westley Richards type" front sight here.
I removed it from a rifle I once owned (not WR) when I shortened the barrel.
It has the fold over sight protector, a fine foresight and a flip up folding night sight.
It has a full band around the barrel.
I doubt it is genuine WR, more likely a reproduction.
Very similar to the foresight on CB's .318 WR rifle in "Safari Rifles", the best photo being in the last set in the book where the rifle is shown with his .470 Andrews a.416 Rigby and a buff head.
If it would be any use for your project you can have it.