Maus45, the M51 is quite easy to do accurately with the tamiya kit. The necessary changes are the rear engine deck with a shaleways one, and some other add on details like the stowage box on the rear and spot light and bits from eastcoast armory. The welded hull is accurate as some m51s were built on m4 large hatch hulls but mist were built on m4a1 76w hulls. That would require either a nick aguilar hull or an old mato plastic m4a1 large hatch hull. Both of which would have to be heavily modified for the turret ring equipment as the tamiya m51 turret has a bigger ring than the tamiya m4 105 turret.
I would really like to do one of these builds too, boy do i have a line up in my head lol.