If the 7.62X51 Spanish Mausers were still available for less than 150 USD in very good condition I'd consider buying one, but anything higher than that would be paying a premium for a reworked rifle that is worth less to me than if it were still in original condition as a 7mm.
I would use only my tailored handloads. If a supply of good condition Boxer primed 7.62 milsurp ammo became available dirt cheap I would buy it only to use as components.

I've run across badly degraded milsurp 7.62 ammo in the past. Some was manufactured using WW2 surplus thick flake type powders that in certain condition breaks down to an acidic dust or mush that eats holes in otherwise good brass cases. It smelled like cankered cat urine. Ammonia dissolves copper based alloys, that's why its used as a bore cleaning solvent. Not something you want inside a cartridge case. Even the gilding metal cladding of steel jackets peeled away.

Funny thing the naked steel jackets were so highly polished and slippery even bone dry that it was difficult to keep a grip on them. They kept jumping from between finger and thumb like wet watermelon seeds or orange pips.