I think that .38 Calibre period ( not any specific .38 Calibre ) was the largest permitted to Civillians to own Arms for in Mexico.

While S & W did not offer any Revolvers chambered for .38 ACP or .38 Super ( until recently ), either Cartridge ( including 9mm Largo and other close relatives ) will fit and fire in almost any regular .38 Special, though of course the pressures of either exceed those of .38 Special, so these are much 'hotter' Cartridges, to the tune of about 26,000 psi and 35,000 psi respectively, if memory serve.

I have never heard of any 'conversions' being done in the old days, to properly allow the use and extraction of .38 ACP or .38 Super in an erstwhile .38 Special Revolver, but I have always felt that S & W and Colt should have offered them.

Since by the early 1930s, both S & W and Colt advertised all of their .38 Special Revolvers to be able to handle the ".38-44" or ".38 - Heavy Duty" Cartridges, and, these often enough enjoyed Ballistics ( 158 Grain Bullet, 1250 FPS ) which we now realize were well into what we would now call .357 Magnum Territory, I am confident that those same Revolvers would manage .38 Super just fine, though only as the now and then thing which their use of .38-44 Cartridges would or should be at most - strictly a now and then thing, and not a steady diet, and done with the appreciation that the Revolver may burst a Cylinder or stretch the Frame...so, not to be taken lightly in my view.