300 wsm oem mag question

i just purchased a 300 wsm barrel . i am building a long range hunting rig . i have a large shank ashburry ( its really a model 12 action ) thick recoil lug . i have a boyds stock magnum contour . i have short action bottom plastic for a plastic tab 308 savage mag . i like the savage mags they have alot of room 3.12 max in the mag box . can i just open the lips on a .308 mag or can i buy the plastic tab mag for the wsm . the goal is to load 208 eldm bullets in the brass cases using the new 6.5 staball powder . in 2.90 oal it gives 2828 or so. i want to load em close to lands and am looking to get the base of bullet out of powder column so i dont loose velocity .

Question 1 can i adjust a 308 mag lips to fit a wsm

question 2 can i get a wsm mag with plastic tab

question 3 is the wsm mag same internal length as the 308 plastic tab mag

Found video on web that has feed lips being opened . Answered my own questions