Doea anybody know about chipping a 92 bronco for"tow mode"

Ford did have electric shift back then; I had it in an '86. I believe at one time you could get a modification from Ford to enable a neutral position. Whether that support for older models is still available... doubtful but you could ask Ford.

I read some accounts that you could remove the electric shift motor and manually shift the Tcase into neutral, or replace the electric shift with a manual lever control.