If you have a typical barrel contour rechambering is not an option. The 9.3x74R is a rimmed cartridge designed for single shot and double barreled rifles and drillings and will not function in a typical bolt action magazine without considerable work. Also the 9.4x74R is over 3.7" long which would require a Magnum size action such as the BRNO 602 or CZ550. As stated by others the factory loads of the 9.3x62 and 9.3x74R are identical 286gr at 2360fps. The 74 has greater capacity to give this velocity at lower pressures in hinged action rifles. Do not assume that you can load the case to pressures it was not designed for. If you want more power than a handloaded 9.3x62,in that bore size ,the 9.3x64 Brenneck is the logical choice.
If you are starting from scratch and you select a standard length action such as the Mauser 98.
The 1905 9.3x62 is hard to beat. If you want more power,the .375 Ruger is ideal. If you can live with a single shot bolt action the 9,3x74R can be built fairly easily.
Here is a comparison of the .375H&H, 9.3x74R and 9.3x62.