the easiest way to tell a trans (auction picture hunting)
the year and the make are going to narrow you down to only 1 or 2 choices. seeing the shift pad in pictures usually can predict the transmission.
there are some skoolie cheat sheets on lengths, motors,..et cetera that can give the options for that make and year. i dont recall the link but it'd be easy to find.
if you have to ask.... its probably a 545