There are a few high-grade traditional-look big game rifles built on the 602 (and the CZ550 BTW) kicking around Australia's Top End for use on buffalo. True, it takes a bit of skilled work to get them looking "vintage" but the results can be worth the extra effort.
Sorry I can't help with action lengths on the others you are interested in, but someone here will know.
Sounds like a great project. Please keep us updated when you get started.
-------------------- Marrakai
When the bull drops, the bullshit stops!
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www.marrakai-adventure.com.au