The plot thickens. I purchased my 58033 from a company called Jensen Auto off of Ebay. I called them and told them the part they delivered did not work for three reasons:
1. The distance between the mounting ears was too great
2. The distance from the front mount to the center of the grooves was too short
3. The service ports on the back vs. top would not be accesible
The compressor I pulled off my Spider clearly is a Sanden SD507 body. Most of the parts sources I have found supply a SD508 or 509 body. I don't know why since these have rear service ports and really are not accesible.
After much searching around I thought I could use a SD507 from a Honda (58567) and convert my Spider to o-rings. Further research found issues with that model (primarily the pulley.)
I sent Jensen Auto some pictures of my compressor and called them to talk about the differences. They indicated they could build me a compressor to meet my needs including one with o-ring fittings versus the OEM flare fittings on my compressor.
I am interested in what other people have found they have for compressors on their Spiders. Talking with Jensen they indicated they have run into this type of issue with other comprssors for Spider customers, and that Alfa seemed to use a number of "kits" to outfit our Spiders with AC, including different compressors.
I should have my new Frankenstein compressor by the weekend, but it will still be awhile before it will be operational.