I did do a calculation of chain wrap for my bike before I ordered the parts. I went into the Shimano website and looked up the specs on the derailleurs for chain wrap capacity. The front is 50T-34T=16T, the new rear cassette will have 32T-12T=20T. 20T+16T=36T. The chain wrap capacity of the long cage 105 derailleur is 37T, so it should be ok. I could have gone for the 11-32, but didn't think I would need higher gears and wanted to play it safe. An 11-34 would not work.

What is ironic is that the original bike components are out of spec. With a 12-27 rear cassette, I get a chain wrap capacity of 31T, but the small cage rear 105 derailleur has a rating of 29T chain wrap on the website.

The problem with the MTB cassettes is that most seemed to have chain wrap numbers of 33T for the small and 45T for the large, and I don't know if they are attached to the bike differently. (I have learned all this in the last week.) Those seemed too small or too big. So, now I will cross my fingers and hope that it works or I am out $200+.