Rudy, firstly, lets clear up the story of the Ferguson engine being a Vanguard car engine. It is not and never was, with the exception of the 23 diesel being fitted to a few Vanguard vehicles. Even in these, they only shared the block, crank and rods. The 23C engine is different again.The petrol engines shared more components but even the blocks are different.
The circlip mentioned is in the injection pump. You locate it after removing the side plate on the pump. As the pump rotates you will notice a series of letters on a wheel towards the rear end of the opening. As each one passes the end of the circlip a scribe mark will line up with the square end of that clip.
Now it has been many moons since I did one of these, but my feeble memory tells me that the letter to have lining up is "E". If the pump has been installed correctly, you fine tune the timing by slackening off the mounting bolts and rotating the body to align the marks.
With good compression and fuel delivery, these engines are no harder to start than any other diesel.
Hope this helps.
Steve.