big bore choice?

[medvedqc]

I hear the M70 in 300 WSM is also a good place to start...

The 'smith would have to do quite a bit of work with the 300WSM. 300 RUM would be better since it's based on the 404J case. The 375H&H is a more logical choice as the barrel channel will need minimal if any modification, boltface is the right size. Feedramp will need a bit of work, and magazine length is perfect. My total cost was $2450 which included the purchase of the donor rifle.
CZ makes the Safari series in 404J. I think you could also use a Remington 30A (M1917) action as well.
Getting a bit off topic though.

if rebarelling better to start with a RUM donor less work than an hh.

yes the cz 550 make a very good choice.

i still think the 458 win mag is a very classical choice and less expensive to build and feed ...