go to the top right hand corner of this page...and there is a link that says "SEARCH"...follow that link
if that doesn't help you to find the ratios in your gearbox you will need to know it gearbox code it will be one of W55, W57 or W58 . You can get this from the ID plate in the engine bay, however if the gearbox has been swapped in the past this may be incorrect...
anyway do a search...
edit: my comments may be a bit rough, at first glance it looked like your were asking what the ratios of the RA60 box were...when at later inspection you may be asking if the ratios in that box will suit an ae86...
If it helps off the top opf my head the T50 ratios are damm close to the W55 ratios... the W57/W58 ratios are slightly longer? (i can never remember if the terminology is shorter or longer )
Anyway I'd just choose a rear end ratio to suit your diving style and car use, rather than choosing the gearbox...