The bolt face is the correct diameter for the 450 Bushmaster and that is not an issue. The issue that can arise is with cartridge feeding and there are solutions for this if it is a problem. The 450 Bushmaster to 98 Mauser swap is a viable and very functional and useful conversion.
I have done 2 98 Mauser barrel swap projects. One fed the 450 bushmaster cartridge flawlessly without modification and the other ended up needing a magazine conversion to feed reliably. I used the Rhineland arms Barrels on both of these swaps. Rhineland uses Green Mountain Barrel Blanks and the barrels are accurate.
I have switched to the Bear Creek Ballistics 450 BM Bullet for handloads in Bolt actions and other non-AR platforms which extends the COL close to a .308 length cartridge and I think these will feed much better in conversions. The Ballistics of their loading that I use speaks for themselves.
https://bearcreekballistics.com/product/450-bushmaster-240-grain-reloading-bullets/Attached is a pic of the first one I did on an Interarms Mauser 98 action and a detachable magazine that allowed it to feed properly as well as a 3 shot group shot with it. The Swarovski Z6 1 x 6 with Warne Bases and KenFarrell Rings works well with this combination. I have used the 450 Bushmaster for the last 2 deer seasons (8 deer) as well as a number of hogs. For 200 yard and closer hunting, which is mostly what I do, the 450 Bushmaster puts them down with authority and so far all have dropped right in their tracks.
The second 450 BM Mauser I did was on a new left hand Zastava Mauser 98 action which feeds flawlessly with no mods.