Which one would I need for a Project 8 3CX ?
Currently i use a genuine perkins branded Mahle T410865, There are sadly 2 copies that look idential one from china and one from Lucas India. They are often advertised under the genuine perkins or mahle part numbers and hard to tell the differance visually but there are often clues in the adverts, words like "replacement for" etc are the normal give aways along with the price.
Mine are currently £225 plus and shipping and Vat genuine perkins branded, although sometimes i get the genuine mahle depends whos got stock and what price.
What you have bought there is a design perkins used between 2003 and early 2005. It was that good so perkins ditched it and started using Iskra, Iskra then changed names a few times and was then bought out by Mahle Group.
There is also a bigger 4.2kw version good for the 4cx or ones with piston hyd pumps that seem to take a lot more effort to crank over than the gear pump ones. Not quite so easy to fit though as solenoid positive stud terminal is 10mm dia not 8mm.