I would just buy some nice envelopes that have a window that matches the 1040. If the SSN is not masked, I would put a blank post it on that section.

SAMPLE - https://www.tenenz.com/category/tax-return-windowed-envelopes/335

I love Tax Tools Among the multitude of really useful tax charts, tables, calculators, form printers, RMD calculator, tax planner, etc it has a wonderful label printer - You select the agency and type of return and it has the address all ready to go. You can then print 1 label anywhere on the sheet or print any number you want starting anywhere on the sheet It can even print an envelope.

For all that it does the price is a bargain.