When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm guessing the A670 would probably be the correct one then. The 40TE is the 4-spd, and I think the other two model #'s are probably 1st-gens, with the 31TH carrying over to the 2nd-gen until the # was changed again to A670 (until the 40TE 4-spd came out). Just a guesstimate.