Just my opinion but it would be best to start with a magnum action. I would do a long action since you have plenty of room to fool with OAL of your ammo.
short action can be done. but you need to buy a new bolt, modify or new magazine, possibly rechamber the old barrel but best to go ahead and change the barrel if you are going that far.
Just my 2 cents
I used a long action for both a 300RSAUM and 7wsm