I picked up a M48A.

I would like to convert this to a 270 Win with a short throat.

I have read that these actions will not work with 06 size cases, but factory 06 rounds fit into the magazine box.

My handloaded 270 loads will not fit, but they are loaded to a longer overall length.

So my question is: Can this be converted safely to 270 Win as long as I keep the cartridge overall length to fit the magazine and just short throat the chamber so the I can keep the bullets close to the lands?

Yes,

Or you can sell the m48a and get a standard action. Then you can load to the cartridge's full potential not hamstring it by keeping the AOL too short.

Most factory loads will likely fit the magazine, except maybe for the heavier weight bullets.

The standard also has the added benefit of having more stocks/styles available for it than the intermediate M48A does.

I bet the feed ramp is much shorter on your m48 than on a std 98, thats probably why the 06 round fits.

No, it fits because the m48A magazine runs about 3.230" and most factory .30-06 ammo despite having a SAAMI AOL of 3.340" is loaded shorter than 3.230". The feedramp may well be shorter but that has nothing to do with the length of an unaltered M48 magazine.