This should be an easy question to answer. I have a long action M70 300 Win Mag(push feed) that I'm thinking about rebarreling/restocking for nice long range rig. However, I can't decide whether to keep it as a 300 Win Mag (I already have a 300 RUM, so don't really need 2) or change it to a 6.5x284. If I choose to move to the 6.5x284, what bolt/action modifications would be necessary? What could I expect to pay for the modifications?

If you change to a 264 Win Mag, all you would need is a rebarrel.

Since you asked... Id buy another rifle