1987 S-15 Manual trans question

I have a 1987 S-15 pickup (GMC version of the Chevy S-10), with L4 2.5l engine & 4-spd manual trans. Trans is acting up & I'm thinking of switching
to a 5-speed. Question is - is there a drop-in replacement for my M73 4-spd, or will I have to replace a lot of other items as well?
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