Hi Cactus,
I take everything I read in the Walthers catalog with a grain of salt, as it can get confusing at times.
The MT 1135 was designed for all the early Life Like units equipped with a plastic coupler retention clip and truck mounted couplers (the 0-6-0 switcher is a body mount), of which the BL-2 is included.
The couplers are long enough to extend through the large gaping hole in the pilots of these units.
The MT 1163 is a body mount conversion for the old style BL-2 and it is designed to fill in the gap in the pilot, and involves cutting the origional coupler mounts away from the trucks.
The MT 1165 and 1166 are similar body mount conversions for the FA2 and GP-18 respectivly, however, it would not supprise me to find that some resourceful modeler had managed to graft one onto an old BL-2.
The MT 1015 is a short shank, wide angle coupler which fits into a draft gear box and can be used on all Life Like and Atlas units featuring a full pilot, as well as on some earlier Kato units.
the following Life Like units use the 1015 coupler:
SD-7
SD-9
SW-9/1200
GP-20
FA1/FB1
C Liner A/B
BL 2 (2001 version)
The MT 1016 comes with a longer shank and can be used if your curves are sharper than 12 inch.
1015 couplers come either unassembled with 2 pairs of 1015 and one pair of 1016 per package as well a a bulk pack with 10 pairs of 1015, or you can get them assembled in either 1015 or 1016 with 2 pairs per package (more expensive that way).
Note that the 1163 does come with 1 pair each of 1015 and 1016 couplers, however, given the cost of the kit as well as the fact that you can't use the pilot fillers, going that route will be a tad more expensive than going with just the 1015/1016.
The Micro Trains web site does not mention the new BL-2 because it is updated only once a month and the new BL-2 has been out for only a couple of weeks.
Expect to see a mention of it maybe after the site has been updated next week, if not next month.
I hope that my reply is not too long winded

, however, Happy Modeling!
Cheers.
Terry