ozhunter's original question was: Is there much difference in the size between a 6.5x54 , 7X57 and 9.3X62 steel rotary mag from the old Mannlicher?
Yes, they differ, and much more than the shape of the cartridge "beds" in the rotor. They differ in length, width and rotor length too. Here are five different Mannlicher-Schoenauer magazines:

Left to right:
M1903 in 6.5x54 length oa 86.4mm width 26.0mm length of rotor 77.8mm
M1910 in 9.5x57 l 86.4mm w 28.6mm rotor 77.8mm
Her the cartridges are guided by the base and bullet nose.
M1924, the so-called "Sequoia model" in .30-06
length 92.9mm wide 28.2mm rotor 84.5mm
This model introduced a cartridge guide ring around the bullets, in front of case necks.
The lengthening of the mag box to the rear necessitated a different, new bolt stop, as the old one would hang out in the air if placed farther back on the receiver.
M1925 in 8x60S length 92.9mm wide 28.2mm rotor 84.5mm
from here on the guide ring is relocated to support the specific case shoulder.
All the post-war Mannlicher-Schoenauers have these long magazines, they only differ in the position of the guide ring and the shape of the much simplified rotors.
M1952 Magnum in 6.5x68 92.9mm wide 28.2 rotor 86.2mm

Another photo of two disassembled magazines for TilleyMan, a M1903 and a 1952 Magnum to show the simplified rotor, and the respective Magazine spring assemblies.

My answer to the original question: No, they are not alike. You can squeeze a 7x57 or 8x57 into the short magazines. Many M1908s were altered or rebarreled for these cartridges. But for longer cartridges like .30-06 or 9.3x62 you need a post-1924 long magazine and action.