Timberghozt - nice idea. I do not have any experience with big bore rifles but here is my $0.02 worth.

I plan to do a similar project in the next couple of years. I would pick the cartridge first & then find the action. If I built a big bore rifle on a Mod 98 action (which is my first choice), I'd go for a classic caliber like a 404 Jeffrey or a 10.75X68 (both use 423 diameter bullet) or even a 450 Rigby. I am not sure if the VZ 24 action will handle these rounds. Since you are planning to do the 338-06 AI anyway, you might want to consider keeping this action for that project & sourcing a large ring Mod 98 action for the big bore (cost about $350?). I saw a recent post on ntiroexpress forum where some one in Australia has built a beautiful 404 Jeffrey on a mod 98 action with nice engraving & fantastic wood work done by Waghorn. I still keep dreaming of that rifle, though I might not have so much engraving on it.

The other issue is sights. If I was planning to hunt with this big bore rifle, I would definitely have GOOD open sights. That seems to be the universal opinion of serious hunters with experience in big bore rifles. I'd also go for a Leupold 1.5-5X scope & have the option of using low power if hunting Dangerous game at close range. I have several Leupolds & 2-7Xs sit on my 222, 7mm08 etc. I have a 1-4X on my 9.3X62 Mauser. I would not need the 7X setting for a big bore rifle. The 375 H&H is the largest caliber that I would use such scope setting for (it is actually a medium bore & not a true big bore) & I would get a 2.5-8X VX3 for that.

Good luck with your project & let us know how you get on.