It took me some time to find this info, so I’ll post it here in-case anyone gets in the same spot as me.
I found that my recently acquired Vita Elan SPA with dual 4HP pumps had one pump unplugged. Plugging it in resulted in the discovery that the pump was locked up. I disassembled and found the impeller failed/exploded on the motor shaft and rubbing on the housings.
The original 56Y framed wet ends for the 4 HP motors are obsolete. The parts themselves are also difficult to locate (and rather expensive) so the general recommendation is just to swap out the whole wet end with something ‘newer’
The newer Vita Spa’s use a 310-1740 wet end (impeller + housing + cover + wear ring + seals). It appears the main difference between the stock older NLA units and the newer 310-1740 is that the output fitting was shorter (new style is a little longer). The threads/mounting/etc. is otherwise the same so it should be a direct swap fit. This is a cross reference from 423038 VITA part number that is listed on their part sheets/catalogs.
Summary:
VITA P/N: 423038
Generic P/N: 310-1740
Description: 56Y Frame 4HP Wet End w/ 2″ inlet/outlet (3.1″ if measured with a tape measure).