Save some dough and go manual
I went with the Raritan PH-II in my Hunter 34, replacing my Jabsco was a no-brainer. I ripped everything head related out and got all new. The PH-II you will find is one of the best heads under 500 bucks.I had to mount a small 12x8x1/2 starboard mounting plate to the liner and then attach the new head to the mounting plate - not difficult just time consuming.Dont let size/shape limit you back to Jabsco. Refit with a better head.You should also think about upgrading your discharge pump while your at it. Also think about hoses while your at it - 1990 hoses are now 17 years old!Oh- make sure you pump out/rinse a couple of cycles for a more "pleasurable" head re-fit project.Good Luck!