Going to replace my power steering gearbox on my 70 Chevelle. Don't know the ratio, comes 21/2-3 turns or 32/3-4 turns stop to stop. can anybody help?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33589&item=2470023905

turn your steering wheel from one side all the way to the other
if you get 3 1\2 to 4 turns you have the standard
if you get only around 3 you have the quick ratio
less turns to go lock to lock

70 was first year for variable ratio. 16:1 on center and 12.4:1 2.9 turns lock to lock.