You've got a great rifle there. I had one in 375H&H which I had rebored & chambered to 416 Rigby. I'm not exactly kicking myself for selling it but I've got bruises on my bruises.

When I see a pic of one like yours the regret goes sky high. I reckon they're a beaut rifle just the way they are, the stock shape works well & looks better.Maybe a Pachmayr decelerator.

& the peep could do with opening up a little. I removed the folding leaf rear sight from mine & used the peep alone. Other than a bit of smoothing up which use does anyway, I can't see they need a great deal of improvenment or customizing. Some don't like the safety. I never found it to be any hassle, you get uesd to it. .404 Jeffery will be a neat calibre for it. Congrats.
Steve