Hello Drew,
Sorry I have not responded to your email yet. I am running behind on my emails. The sedan brackets are indeed different than the SLs. Much simpler, lighter, easier to deal with during repairs to the engine, only one AC belt is needed, and AC belt adjustment is simpler. The reason for the difference in sedans and SLs, is sedans have more hood clearance than the SLs so the compressor had to go below on the SLs. Back then those old monstrous Tecumseh and York upright compressors were large and needed a lot of room. With the new rotary Sanden style compressors you can find enough room for the compressor on the top and can still leave the alternator in its original position below. The SL "monster bracket" can be removed and replaced by the simpler sedan bracket. I am in the middle of a change-over right now so I can post some pics if you like. Tom Kaiser has also used my sedan bracket change-over as well as others with good results. I think Tom has his work well-documented, maybe he can chime in also. The alternative is to leave the original monster bracket on the engine, purchase the "upright" to Sanden adapter and just bolt the Sanden compressor below. I'll try to get back with some pics soon.