Rear wiper motor 3/4" or 1" spline?

[ckomai]

I'm going to buy a new motor on ebay for my rear wiper. Looks like they are advertising a 3/4" spline and 1" spline even though they both are for 91-94 explorers. Which do I get?

 

[Anime]

91's should have the smaller spline unless it was replaced. It wasn't until the later 93-94 model that some started to have the larger 1" spline.