The 06 and 300 win mag have different size case heads. Your bolt has a M16 style extractor and I think that would cause you problems if you tried to open the bolt face. I'm sure a gunsmith could answer that for you.
There is a variety of wildcats based of the 30-06 case that would do quite well. My dad has his 6.5-06ai built off a Howa long action and it shoots VERY well.
Find a gunsmith that has worked with Howa's like Kevin Cram www.montourcountyrifles.com
and you will have a great shooter I'm sure.