I don't know about 450.
Can you measure the starter nose or crankcase hole? (accurately)
If it's about 1.800" it will fit but depth may need modifying?
I have one plug ready if anyone want's it and can make one in the morning tomorrow before I go to work.
I'm having second surgery on my arm on 8th June and don't know when I'll be able to make anything after that, got a lot of stuff to do in next few weeks
i'll measure next weekend, or tomorrow if I have a second. What specifics do you need? Diameter only, or more info? I was recently looking into plugging up the hole for mine and was thinking of using a brass freeze plug, but your option looks great.
I have a few made, can supply slightly different diameters (only a few thousandths of inch difference)
CB350 seems to be smaller than 360 by about 0.003"~0.005", still don't have a CB450 case to measure but it looks like it's same as 360