Re: perkins 4.107 / 4.108
Celestialsailor is correct. I helped a friend pull a paragon from a 4.107. you might have to unbolt the engine and slide it forward a bit. Be sure to support it. My friend trashed his Paragon and installed a Borg Warner, which by the way I have an extra one along with a bellhousing. You'll have to change the flex plate. The entire assembly may be a slightly different length.
PM me if you're interested ... I'm in Southern California
Lowell - s/v Chasing Summer - Spencer 42/hull 17 ... happy sailing