Get the smaller one AND the video
Lindy,
If I understand your question, you want to purchase a Loos Tension gauge for your husband as a present, but don't know the wire size of of the rigging of an Ericson 32 to be able to tell which Loos tension gauge is the right size for your boat? (And you haven't come up with a clever way to ask "Just how big is the headstay on our boat anyway?" that won't raise questions.)
Assuming the wire rigging hasn't change on the older vs the newer models, I can tell you that the largest wire size on a newer Ericson 32 is 9/32". And that would suggest you go for the larger of the standard Loos Tension gauges, Model 90F, for 3/16-9/32" wire, Boat US #179366 for $62.99. And if he is at all new to rig tuning, I highly recommend that you also purchase Brion Toss's video on rig tuning, which I found to be a godsend. West Marine and Boat US don't seem to carry it anymore, so go to the web site that Sean mentioned (
http://www.briontoss.com/ ) in the catalog section, under videos, then more products, and click on the Tuning Your Rig video.