op
i agree with those saying don’t tube roll until you have at least 50-100 hrs time to burn in your new piece and the tubes
5751 are lower gain 12ax7 -- you can also step down to 12au7 (even lower gain)... how it affects the sound of your aric can only be learned by trying, no shortcuts available... leaving aside a different volume control setting which would likely result
fyi - I have many many of these small signal tubes pairs that have been accumulated over the years, happy to assist if/when you are ready to roll some (it is a lot fun, but as some have mentioned, it is its own rabbit hole of sorts)
among best of breed old stock 12v signal tubes, in my experience, you should look to at sylvania/amperexes among the usa made tubes, and telefunken/siemens/philips/tungsram among euro made ones

