We are using our Alphatross with Shell Diala Oil AX instead of the Low Odor Base Solvent that was supplied by NEC. We have a few hundred gallons of this oil on hand, which made it more cost effective to replace the pump than to purchase the 8 or so gallons of LOBS ($93.30/gallon on 2021-08-09). The transformer oil is much more viscous than the LOBS, (9 mm2/s vs 0.1 mm2/s at 40°C), necessitating a larger pump to maintain adequate flow. March suggested going with an AC-4C-MD 115V with trim to 2.5 inches. The original system from NEC shipped with a March AC-3CP-MD-115VAC.
March pump page: https://www.marchpump.com/pump/ac-4c-md-magnetically-coupled-pump/ March curves page: https://www.marchpump.com/wp-content/uploads/2019/06/March-Series-4-Pump-Curve.pdf March pump manual: https://www.marchpump.com/wp-content/uploads/2019/06/pump-manual-acandbc4-0145-0023-1000-rev30.pdf 2D Drawing: https://www.marchpump.com/wp-content/uploads/2019/06/March-AC-4C-MD-115V-Pump-Drawing.pdf Installation guide: https://www.marchpump.com/wp-content/uploads/2019/07/march-pump-general-installation-guide-0750-040.pdf
March also provided us with a 3D model in STEP format for use in our modeling.