Does a transmission of a 1990 nissa pickup fit for a 1996?

Hello, It is not likely the two are compatible since 1996 was the first year of OBD-II, meaning there were more requirements for standardized electronic equipment. There is a good possibility of the two bolting up without issues, however, you may find there are plenty of differences. Check your part number and see, or contact a salvage, but don't get your hopes up.